# Radical | Bra Fitting Encyclopedia *Source: https://wearingradical.com/encyclopedia/ ยท Last updated November 2, 2026* --- Reference # Bra Fitting Encyclopedia A comprehensive, fact-checked reference for understanding bras and bra fitting. Last updated November 2, 2026 ## Table of Contents 1. [Overview and How to Use This Encyclopedia](#overview) 2. [Bra Anatomy: Understanding the Parts of a Bra](#anatomy) 3. [How to Measure Yourself for a Bra](#measure) 4. [How to Put On Your Bra](#put-on) 5. [How Bra Sizing Works](#sizing) 6. [How to Tell If Your Bra Fits](#fit-check) 7. [Cup Size Reference Chart](#cup-chart) 8. [Sister Size Reference Table](#sister-sizes) 9. [Fit Adjustment Reference Table](#fit-adjustments) 10. [Breast Shape and Fit](#shape) 11. [Quick-Reference Fit Summaries](#quick-ref) 12. [Between Sizes: When Measurements Don't Line Up](#between-sizes) 13. [Sizing Conflicts and Reconciliation Notes](#conflicts) 14. [Recommended Sources](#sources) ## 1. Overview and How to Use This Encyclopedia This encyclopedia is a purely educational reference for understanding how bras work, how to measure yourself for a bra, how bra sizing functions, and how to assess whether a bra fits properly. It is designed to be accessible to anyone, regardless of prior knowledge or experience. **What this encyclopedia covers:** - The parts of a bra and what each one does - Step-by-step measurement instructions using a soft tape measure - How to put on a bra correctly before assessing fit - How band sizes and cup sizes are calculated - How to check whether your bra fits, broken down by band, cups, and straps - Reference tables for cup sizes, sister sizes, and fit adjustments - How breast shape affects fit beyond size alone - Quick-reference summaries for fast fit checks - What to do when your measurements fall between sizes - Notes on where sizing systems and methods disagree - Recommended external sources for further learning **What this encyclopedia does not cover:** - Brand recommendations or product suggestions - Medical advice, surgical guidance, or breast health diagnostics - Shopping or purchasing guidance - Specific bra styles or construction recommendations **Important:** The measurement and fitting methods described here are educational guidelines, not universal rules. Bra sizing varies across brands, countries, and individual body shapes. Always prioritize comfort and personal fit over any calculated size. If you have medical questions about your breasts, please consult a healthcare professional. ## 2. Bra Anatomy: Understanding the Parts of a Bra Before diving into measurement and fit, it helps to know the names of the parts of a bra. The fit guides in this encyclopedia use these terms, so you can refer back here any time. ### The Band The band is the horizontal piece that wraps around your ribcage. It includes the back wings (the side panels that stretch around your torso) and the closure (hooks and eyes). Some bras also have a cradle, a fabric panel that holds the cups and wires in place on the front of the band. The band provides most of the bra's support and should carry the weight of your breasts, not the straps. ### The Cups The cups are the fabric or molded material that holds each breast. The top edge of the cup is called the neckline or decollete. The point where the strap attaches to the cup is called the apex. Cups can be seamed (made of multiple fabric panels sewn together) or seamless (molded from a single piece of fabric). Seamed cups generally offer more shaping and support for larger busts, while seamless cups offer a smoother look under clothing. ### The Gore The gore is the center piece of the bra that sits between the cups. On a wired bra, the gore should lie flat against your sternum (breastbone). If the gore lifts away from your chest, the cups are likely too small. On a wireless bra, the gore may not touch the sternum, but it should not float excessively far from it. ### The Straps The straps run from the cups over your shoulders to the back band. They provide a smaller share of support and mainly keep the cups positioned. Straps should be adjustable and should not dig into your shoulders or slip off. Most bras have sliders (small adjustable hardware) on the straps for length adjustment. ### The Underwire The underwire is a thin metal or plastic wire sewn into the bottom of the cup that separates and supports breast tissue. It should sit exactly at the breast root, where your breast meets your chest wall. The wire should not sit on breast tissue, and there should be no gap between the wire and your ribcage. Not all bras have underwires; wire-free bras rely on the band and fabric structure for support. ### The Hooks and Eyes The closure system on the back of the bra. Most bras have two or three columns of hooks so you can tighten the band as it stretches over time. Always start on the loosest column when the bra is new. ### The Channeling The fabric tunnel that holds the underwire in place inside the cup. If the wire is poking or slipping, the channeling may be damaged or the wrong size for the wire. ## 3. How to Measure Yourself for a Bra This guide walks you through measuring yourself for a bra at home. You will take six measurements total: three underbust and three bust measurements. The method uses a simple averaging technique to arrive at your starting band and cup size. ### What You Will Need - A soft, flexible measuring tape (not a rigid carpenter's tape) - A mirror (to check tape placement) - Remove your bra and any top for the most accurate measurements, if possible **Why measure without a bra?** Measuring on bare skin eliminates interference from padded cups, underwires, or compression bands that can distort your measurements. If you cannot measure without a bra, wear an unpadded, non-minimizing bra and note that your results may be slightly less accurate. ### Step 1: Measure Your Underbust (Band Size) Take three underbust measurements, each at a different level of snugness: ### 1. Comfortably Snug Underbust Wrap the tape measure snugly around your ribcage, directly under your breasts. The tape should feel firm but not uncomfortable. Keep the tape level all the way around, parallel to the floor. - Stand upright and relaxed - Keep the tape level and untwisted - If it helps, wrap the tape around your back first, then hold both ends in front to read the number ### 2. Tighter Underbust Pull the tape tighter than the snug measurement, but still comfortably. This gives a sense of how compressible your ribcage is. ### 3. As-Tight-As-Comfortably-Possible Underbust Pull the tape as tight as you can while still breathing comfortably. This measurement helps determine whether your ribcage is firm or compressible, which can affect band size selection. **Average the three underbust measurements.** Round the average to the nearest even number to get your band size. For example, if your average is 31.25 inches, round to 32. If your average is 35.0 inches, your band size is 34 or 36 depending on the rounding convention. **Band rounding note:** The nearest-even-number rule is a simplification. Some fitting methods (such as the r/ABraThatFits community calculator) use a more nuanced approach that considers the difference between your snug and tight measurements. If your snug and tight underbust measurements are less than 2 inches apart, your ribcage is firm and you may prefer sizing up. If the difference is 4 inches or more, your ribcage is compressible and you may prefer sizing down. See [Section 12: Between Sizes](#between-sizes) for more detail. ### Step 2: Measure Your Bust (Cup Size) Take three bust measurements around the fullest part of your breasts: ### 1. Standing Bust Stand upright and wrap the tape around the fullest part of your bust, usually at nipple height. Keep the tape level. - Do not press down into the tissue - If your fullness sits lower than nipple height, measure at that lower point - Use the mirror to keep the tape level - If your breasts are different sizes, that is normal. Just wrap the tape around your bust as usual ### 2. Leaning Bust (90 Degrees) Bend forward 90 degrees at the waist so your breasts hang forward. Measure around the fullest part. This captures tissue that may not be fully captured while standing, especially for pendulous breasts. ### 3. Lying-Down Bust Lie flat on your back and measure around the fullest part of your bust. This position redistributes tissue differently and provides a third data point for averaging. **Average the three bust measurements.** ### Step 3: Calculate Your Bra Size Subtract your average underbust measurement from your average bust measurement. This difference is your **cup difference**. Use the cup chart in [Section 7](#cup-chart) to find your cup size based on this difference. Pair your rounded band size with your calculated cup size to get your final bra size. For example, if your band is 32 and your cup difference is 4 inches, your size is 32D. **Worked example:** - Underbust measurements: 31 snug, 30 tight, 29 very tight. Average = 30.0. Rounded band = 30. - Bust measurements: 36 standing, 37 leaning, 36 lying. Average = 36.3. - Cup difference: 36.3 - 30.0 = 6.3 inches. This falls between F (6") and G (7"). - Starting size: approximately 30F or 30G, depending on rounding preference. ### Fit Accuracy Tips - If the tape slips down, it is too loose - If you cannot breathe comfortably, it is too tight - Use a mirror to check the tape stays level - You can wrap the tape around your back first and bring the ends together in front to read the number - Keep the tape untwisted for maximum accuracy ### Optional Context You can also note: - Your current bra size (for comparison) - Any fit issues you are experiencing, such as gaping or spillage - Recent body changes, such as those related to pregnancy, nursing, or surgery (these can affect your measurements) These details are optional but can help you interpret your results more accurately. ### When Measurements Seem Off If your results seem strange, here are some things to check: - **Your bust measurement is smaller than your underbust:** This can happen with smaller busts. The cup difference will be zero or negative, which corresponds to an AA or A cup. This is normal. - **Your leaning bust is much larger than your standing bust:** This is common with pendulous breasts. The leaning measurement captures tissue that hangs forward. The averaging method accounts for this. - **Your three underbust measurements are very different:** A large gap between snug and very-tight measurements means your ribcage is compressible. A small gap means it is firm. Both are normal. See the band rounding note above and [Section 12: Between Sizes](#between-sizes) for guidance. - **Your result is very different from your current bra size:** This is common and does not necessarily mean either measurement is wrong. Many people are wearing the wrong size. Try the new size and assess comfort. - **Your measurements seem inconsistent across sessions:** Re-measure. Small differences in tape placement or posture can change measurements by half an inch or more. ## 4. How to Put On Your Bra This guide explains how to put on a bra correctly before checking the fit. Using the right technique helps make sure your bra feels and functions the way it is meant to, and keeps the band in good shape over time. ### Step 1: Loosen the Straps Start by fully loosening both bra straps. You will adjust them later once the band and cups are in place. ### Step 2: Clasp the Bra You have two main options: #### Option A: Behind Your Back (Recommended if you can reach) - Slip your arms into the straps like a backwards vest - Reach behind and clasp the bra on the loosest hook - Why the loosest hook? It helps preserve the stretch of the band over time. As the band stretches with wear, you can move to tighter hooks to maintain fit #### Option B: Front-Rotate Method (If clasping behind your back is not comfortable) - Wrap the bra around your torso backwards, with cups facing your back - Clasp it on the loosest hook - Gently rotate the bra so the cups come to the front - Slip your arms through the straps *Note: This method can stretch the band more quickly, so rotate gently.* ### Step 3: Position the Cups (Scoop and Swoop) Bend forward slightly. Then, for each side: 1. Use one hand to swoop breast tissue inward toward the center 2. Then scoop it up into the cup 3. Make sure no tissue is sitting below the wire (or base of the cup if wireless) 4. Use your finger to check along the bottom edge. You should feel only ribcage, not breast tissue Also check the outer edges of the cups near your armpits for any tissue that has been missed. Re-scoop if needed. **What is scoop and swoop?** The scoop and swoop is a technique for positioning all breast tissue inside the bra cups before assessing fit. It involves using your hand to sweep tissue from under the band, from the sides, and from underneath the cups, then lifting it into the cup. This ensures the cup is actually containing all your tissue, which is essential for an accurate fit assessment. ### Step 4: Adjust the Underwires (If your bra has them) Underwires should sit exactly where your breast meets your chest. This point is called the **breast root**. There should be no space under the wire and no breast tissue underneath it. If your breasts are fuller or pendulous, lean slightly forward to help the wire sit properly before scooping and smoothing tissue into place. ### Step 5: Leave the Straps for Last Do not tighten your straps yet. Straps should not be used to lift your breasts. The band should do most of the support work. You will adjust the straps during your fit check. **Why this order matters:** If you tighten straps before the band and cups are positioned, you may compensate for a poor band fit with overtightened straps, which can cause shoulder discomfort and give a false impression of support. Always position band and cups first, then fine-tune straps. ## 5. How Bra Sizing Works Bra sizing can feel confusing, but the system is built on two simple components. This guide explains band and cup sizes, how sister sizes work, and what to do if your bra does not fit. ### What Makes Up a Bra Size A bra size has two parts: - **The band size** (a number like 32 or 34) - **The cup size** (a letter like A or D) Your band size comes from measuring around your ribcage. Your cup size is based on the difference between your ribcage and your bust. ### Understanding the Band Size Your band size is the number in your bra size (like 30 or 36). It is measured by wrapping a tape snugly around your ribcage, just under your breasts, and rounding to the nearest even number. Example: If your ribcage measures 29 inches, round to 30. If it measures 31.25 inches, round to 32. The band provides most of the bra's support, so it should feel snug and secure, but not painful. **How much support comes from the band?** Sources commonly cite that the band provides approximately 80 to 90 percent of a bra's support, with straps providing the remainder. However, this percentage is not a universal or precisely measured figure. It varies with bra style, body shape, and construction. Treat it as a general principle: the band, not the straps, should be doing the heavy lifting. ### Understanding the Cup Size Your cup size is the letter in your bra size (like B, D, or G). Here is how to calculate it: - Measure around the fullest part of your bust, without pressing down - Subtract your band size from your bust measurement - The difference tells you your cup size Example: Bust = 36 inches, Band = 32. 36 - 32 = 4 inches. Cup = D. Size = 32D. **Important: Cup size depends on the band.** A 32D and a 36D do not have the same cup volume. Cup size is a ratio proportional to band size. A 28E is much smaller than a 36E. There is no such thing as a fixed "D cup." This is why sister sizing works (see below). ### Understanding Sister Sizes If your bra is close but not quite right, try a sister size. Sister sizes have the same cup volume but a different band size. To keep the same cup volume: - Go up a band size, go down a cup size (34C to 36B) - Go down a band size, go up a cup size (34C to 32D) This is helpful when: - The band feels too tight, but the cups fit - The cups fit, but the band rides up or feels loose ### Adjusting Bra Size Based on Fit If your current bra does not fit well, use the table in [Section 9](#fit-adjustments) to determine how to adjust your size. ### Re-measuring Re-measure every 6 to 12 months. Your size can change due to weight fluctuations, hormonal changes, aging, pregnancy, nursing, or surgery. A bra that fit last year may not fit this year. ### The +0 vs +4 Sizing Debate Older bra-fitting guides commonly added 4 or 5 inches to the underbust measurement to calculate the band size. For example, a 29-inch underbust would become a 34 band (29 + 5 = 34). This is sometimes called the "+4 method." Modern fitting methods, including the r/ABraThatFits community calculator, use a +0 approach. The band size is close to the raw underbust measurement, rounded to the nearest even number. A 29-inch underbust becomes a 30 band. This difference is why modern methods often produce much larger cup sizes and smaller band sizes than older methods. If you have been wearing a 34B using the +4 method, the +0 method might suggest a 30D or 30DD. The cup volume is similar, but the band is snugger and the cup letter is higher. This encyclopedia uses the +0 approach. If your current bra size was calculated using the +4 method, your measurements using this guide may suggest a very different size. This is expected and does not mean the old size was wrong, only that the method was different. ## 6. How to Tell If Your Bra Fits This step-by-step guide helps you check if your bra fits properly and understand what each part of the bra is supposed to do. Always check in this order: **band first, then cups, then straps.** ### What You Will Need - A bra (preferably newer) - A mirror ### Before You Start 1. Loosen the straps 2. Clasp the band on the loosest hook 3. Scoop and swoop your breast tissue fully into the cups, especially from the sides and underneath ### 1. Check the Band Fit The band provides most of your bra's support, so start here. - The band should sit level and parallel to the floor, not ride up toward your shoulders - On a new bra, use the loosest hook - Test it by sliding two fingers under the band at your back. It should feel snug but not too tight - Lift and lower your arms. The band should stay in place without shifting #### Optional band tests: - **Strapless test:** Take off the straps but keep the band on. It should still hold firmly - **Upside-down test:** Turn the bra upside down and clasp it mid-back. It should stay snug without the cups #### Signs you may need a larger band size: - You struggle to clasp the band on the loosest hook - The band feels too tight or painful - You get red marks or pinching on your skin #### Signs you may need a smaller band size: - You can pull the band more than about two inches from your back - The band rides up toward your shoulders - The band shifts or feels loose when you move your arms ### 2. Check the Cup Fit Once the band fits well, check the cups. - Make sure all breast tissue is inside the cups using the scoop and swoop method - Run your finger along the bottom edge of the cups, especially under your armpit. You should feel bone (ribcage), not breast tissue - For wired bras, the gore (the center piece between cups) should lie flat against your sternum without digging in or floating - For wire-free bras, the gore should be comfortable and not float too far from the sternum #### How to double-check for spillage: - Look at your side view in the mirror. You will often catch spillage there - Try putting on a tight shirt. If you can see a bulge where the top of the cup ends, that is a sign of spillage #### Signs you may need a larger cup size: - Breast tissue spills over the tops of the cups after scooping and swooping - The gore (for a wired bra) lifts away from your sternum - Your breasts feel compressed or suffocated #### Signs you may need a smaller cup size: - There is empty space or gaping in the cups, even after scoop and swoop - The cups wrinkle or do not sit smoothly against your breasts **Note about asymmetry:** If one breast is larger, fit the larger breast fully in the cup. In the next step, tighten the strap on the smaller breast's side to bring that cup closer to your body. Asymmetry is common and normal. ### 3. Check the Strap Fit Straps provide a smaller share of support and keep cups in place. - Slide your index finger under each strap from cup to band. It should feel snug but comfortable - Lift the strap upward. It should only move about one inch before feeling secure - Most people prefer straps at the midpoint of their shoulders, but choose what feels best for you #### Adjusting for asymmetry: Shoulders and breasts are often asymmetrical. Tighten the strap on the smaller breast side to bring that cup closer to your body. #### Strap fit signs: - If straps keep slipping off your shoulders, check the band first: slipping straps usually point to a band that is too big, or a style that does not suit your shoulder shape - Loosen straps if they dig into your shoulders or leave marks ### Tips for Success - Always check band first, then cups, then straps - Check fit when your body is relaxed and arms are down - If your bra is older and the band feels loose, try clasping on a tighter hook - Asymmetry is common and normal. Adjust straps independently for each side - A well-fitting bra should feel snug on the loosest set of hooks if the bra is less than a year old - Comfort is the primary criterion. If something feels wrong, trust your body over any calculation ## 7. Cup Size Reference Chart The chart below shows the US cup sizing convention, where each inch of difference between bust and band corresponds to one cup letter. This is the most common system used in the United States. | Difference (Bust minus Band) | US Cup Size | UK Cup Size (for comparison) | | --- | --- | --- | | 1 inch | A | A | | 2 inches | B | B | | 3 inches | C | C | | 4 inches | D | D | | 5 inches | DD or E | DD | | 6 inches | DDD or F | E | | 7 inches | G | F | | 8 inches | H | FF | | 9 inches | I (or HH) | G | | 10 inches | J | GG | | 11 inches | K (or I) | H | | 12 inches | L (or K) | HH | **US vs UK sizing:** The US and UK cup letter systems match through DD and diverge above it. The same physical cup volume may be labeled differently depending on which system a brand uses. For example, a US "DDD/F" is roughly equivalent to a UK "E." If you are shopping internationally or buying from a UK-based brand, always check which sizing system the brand uses. The r/ABraThatFits community recommends UK sizing for its more consistent letter progression. **Chart conflicts:** The source material contained two slightly different cup charts. One version maps 6 inches to F and 9 inches to I; another maps 6 inches to DDD or F and 9 inches to HH or I. The chart above represents a reasonable reconciliation. See [Section 13: Sizing Conflicts](#conflicts) for details. ### Key Principles - Cup size is a ratio proportional to band size. A 28E is much smaller than a 36E - There is no such thing as a fixed "D cup." Cup size depends entirely on band size - Many people underestimate their cup size. Going from a 32B to a 28E is normal, not a mistake - The one-inch-per-cup convention is broadly used in US sizing, but some brands use their own systems ## 8. Sister Size Reference Table Sister sizes share the same cup volume but have different band sizes. Moving along a row keeps cup volume constant while changing the band. | Band | Sister sizes (same cup volume) | | --- | --- | | 28 | 28DD, 30D, 32C, 34B, 36A | | 30 | 30DD, 32D, 34C, 36B, 38A | | 32 | 32DD, 34D, 36C, 38B, 40A | | 34 | 34DD, 36D, 38C, 40B, 42A | | 36 | 36DD, 38D, 40C, 42B, 44A | | 38 | 38DD, 40D, 42C, 44B, 46A | | 40 | 40DD, 42D, 44C, 46B, 48A | ### How to Use Sister Sizing - **Band too tight, cups fit:** Go up a band, down a cup (34C to 36B) - **Band too loose, cups fit:** Go down a band, up a cup (34C to 32D) - **Band fits, cups too small:** Go up a cup (34C to 34D) - **Band fits, cups too big:** Go down a cup (34C to 34B) ## 9. Fit Adjustment Reference Table If your current bra does not fit well, use this table to determine how to adjust your size. These are general patterns, not universal rules. Always try the new size and assess comfort. | Current Problem | Adjustment | Example | | --- | --- | --- | | Band fits, cups too small | Go up a cup size | 34B to 34C | | Band fits, cups too big | Go down a cup size | 34B to 34A | | Band too big, cups fit | Down a band, up a cup (sister size) | 34B to 32C | | Band too small, cups fit | Up a band, down a cup (sister size) | 34B to 36A | | Band too small, cups too small | Up a band, keep cup letter | 34B to 36B | | Band too small, cups too big | Up a band, down 2 cup sizes | 34B to 36AA | | Band too big, cups too big | Down a band, keep cup letter | 34B to 32B | | Band too big, cups too small | Down a band, up 2 cup sizes | 34B to 32D | **Common pattern: "Band too big, cups too small"** This is one of the most common fit problems. The fix is to go down one band size and up two cup letters. Examples: - 32A to 30C - 36B to 34D - 34D to 32DDD/F The logic: first find your sister size (smaller band, same cup volume), then size up the cup. For example, 32A to 30B (sister size), then 30B to 30C (up a cup). Result: 30C. ## 10. Breast Shape and Fit Two people with the same bra size may find that the same bra fits one and not the other. That is because bra fit depends on more than the numbers. Breast shape, how the tissue sits on the chest, and how firm or soft the tissue is all affect which bras will work. This section covers the key shape concepts that influence fit. ### Projection vs. Shallowness **Projection** refers to how far the breast projects forward from the chest wall. A projected breast sticks out more, while a shallow breast sits flatter against the chest. A bra designed for shallow breasts may not have enough depth at the apex for a projected breast, causing the cups to feel too small even when the size is technically right. Conversely, a bra designed for projected breasts may have too much depth for a shallow breast, causing gaping or wrinkling at the top of the cup. If you find that cups always seem too shallow or that your tissue pushes the bra away from your chest wall, you may need bras designed for more projection. If cups always gap at the top, you may need bras designed for shallower shapes. ### Fullness Distribution Breasts can be fuller on top, fuller on bottom, or evenly full. This affects which cup styles work. - **Top-full:** More tissue sits above the nipple. Cups that cut in at the top may be too low. Styles with more coverage at the top of the cup may work better. - **Bottom-full:** More tissue sits below the nipple. Cups may gap at the top, especially in molded or full-cup styles. Styles with less coverage at the top may accommodate this shape better. - **Even fullness:** Tissue is distributed fairly evenly. Most cup styles may work, but fit still depends on other shape factors. ### Root Width The root is where the breast attaches to the chest wall. A wide root means the breast tissue extends further toward the underarm. A narrow root means the tissue is more centered on the chest. This affects which underwire shapes will be comfortable. A bra with wires that are too narrow for a wide root will sit on tissue at the sides. A bra with wires that are too wide for a narrow root will have empty space at the sides of the cups. ### Why This Matters If your calculated size does not seem to work in any bra you try, shape may be the reason. The same cup letter can fit very differently depending on whether the bra is designed for projected or shallow, top-full or bottom-full, wide-rooted or narrow-rooted shapes. This is why comfort, not just the number on the tag, is the ultimate test of fit. ## 11. Quick-Reference Fit Summaries Short-form guidance for checking bra fit. Use this as a fast checklist when you do not have time for the full step-by-step guide. ### 1. The Band - The band should be snug and sit level, parallel to the floor across your back - The band provides most of the bra's support, not the straps - You should be able to just slide two fingers under the band at your back - When you lift and lower your arms, the band should stay in place without shifting ### 2. The Cups - The cups should fully encapsulate all your breast tissue - Scoop and swoop your breast tissue so it sits inside the cups, not spilling out below the bottom edge - When you run your finger along the bottom edge of the cups up to your armpits, you should feel ribcage, not breast tissue - After ensuring all tissue is inside the cups, the tissue should sit flush against the tops of the cups - For wired bras, the gore (the center piece between cups) should lie flat against your sternum, not digging in or floating ### 3. The Straps - Adjust straps to your preference, which may be different for each shoulder - Straps provide a smaller share of support and keep cups in place - When you lift a strap above your shoulder, it should only move about one inch before feeling secure - If straps slip off, check the band first: slipping straps usually point to a band that is too big. If they dig in or leave marks, loosen them ## 12. Between Sizes: When Measurements Don't Line Up The nearest-even band rounding rule gives a starting point, but it does not work perfectly for everyone. This section covers what to do when your measurements fall between sizes or your ribcage profile is unusual. ### Snug vs. Tight Underbust The difference between your snug and very-tight underbust measurements tells you how compressible your ribcage is: - **Less than 2 inches apart:** Your ribcage is firm. You may prefer to size up to the next even band for comfort. - **2 to 4 inches apart:** Average compressibility. The nearest-even rule should work well. - **More than 4 inches apart:** Your ribcage is compressible. You may prefer to size down for a snugger, more supportive fit. ### Smaller vs. Larger Bands - **Smaller bands (32 and under):** These bands have less fabric and less stretch, so they can feel tighter at the same snugness. If you are between sizes, rounding up may be more comfortable. - **Larger bands (36 and above):** These bands have more fabric and tend to stretch more. If you are between sizes, rounding down may provide better support. ### How This Compares to the r/ABraThatFits Calculator The ABTF community calculator uses a more nuanced algorithm that considers all six measurements rather than simple nearest-even rounding. It generally selects a band size near the snug underbust, often about 2 inches larger than the tight measurement, and uses a +0 approach. If you are between sizes or have an unusual ribcage profile, the ABTF calculator may give a more tailored result. You can use it at [abrathatfits.org/calculator](https://www.abrathatfits.org/calculator). ## 13. Sizing Conflicts and Reconciliation Notes Different sources sometimes disagree on sizing details. This section documents the known conflicts and how they have been reconciled in this encyclopedia. ### Conflict 1: Cup chart mapping **The issue:** The source material contained two slightly different cup charts. One maps 6 inches to F and 9 inches to I. Another maps 6 inches to DDD or F and 9 inches to HH or I. **Reconciliation:** The chart in [Section 7](#cup-chart) uses the DDD/F and HH/I mappings, which are more commonly seen in US sizing. Both versions are noted for transparency. ### Conflict 2: Band support percentage **The issue:** The source material states the band provides "about 90%" of support and straps "about 10%." External sources cite varying figures: 80%, 80-90%, 90%, or 70%. **Reconciliation:** This encyclopedia uses "commonly cited as 80 to 90 percent" rather than a fixed 90%. The exact percentage varies by bra style, body shape, and construction. The key principle is that the band, not the straps, should provide most of the support. ### Conflict 3: Band rounding method **The issue:** The source uses nearest-even-number rounding. The r/ABraThatFits community calculator uses a more nuanced algorithm based on all six measurements. **Reconciliation:** The nearest-even rule is presented as a simplification, with a note directing readers to the ABTF calculator for a more tailored result. See [Section 12](#between-sizes) for guidance on between-sizes situations. ### Conflict 4: US vs UK cup sizing **The issue:** The source material uses US cup letters. The ABTF community recommends UK sizing for its more consistent progression above D. **Reconciliation:** The cup chart in [Section 7](#cup-chart) includes both US and UK columns. Readers are advised to check which system a brand uses before purchasing. ### Conflict 5: Cup calculation basis **The issue:** One version of the source calculates cup size using the raw average underbust measurement. Another uses the rounded band size. These can give slightly different results. **Reconciliation:** This encyclopedia uses the rounded band size for cup calculation, which is the more common method. If you are between cup sizes, try both and see which fits better. ## 14. Recommended Sources The following sources are recommended for further bra-fitting education. ### Primary Recommended Sources | Source | URL | What It Covers | | --- | --- | --- | | r/ABraThatFits (Reddit community) | https://www.reddit.com/r/ABraThatFits/ | Community-driven bra fitting advice, fit checks, and discussion | | r/ABraThatFits Beginner's Guide | https://www.reddit.com/r/ABraThatFits/wiki/beginners\_guide/ | Step-by-step beginner's guide to bra fitting, including the six-measurement method, scoop-and-swoop, gore tacking, sister sizing, and shape concepts | | A Bra That Fits Calculator | https://www.abrathatfits.org/calculator | Online calculator using the six-measurement method with UK sizing | | Bratabase | https://www.bratabase.com/ | User-built database for bra measurements, comparisons, reviews, and fit photos | | Bustyresources Wiki | https://bustyresources.fandom.com/wiki/Bustyresources\_Wiki | Community wiki with guides on bra sizing, sister sizes, scoop-and-swoop, and bra shape | **Source quality note:** The sources listed above are community-driven or database resources. They are widely regarded in bra-fitting communities but are not peer-reviewed academic sources. Always cross-reference and prioritize comfort over any single source's recommendation.