How to Find Your Bra Size at Home: A Simple Fitting Guide
By Shop Women's Bras, Panties & Lingerie Online | Published: 2026-10-13
Category: Guides pratiques
Measure your band and bust at home, then convert those numbers into a bra size with a simple two-step method and a fit check that catches common sizing mistakes.
Quick answer
Measure your band size by wrapping a soft tape snugly around your ribcage directly under your bust, then measure your bust at the fullest point. Subtract the band measurement from the bust measurement: each inch of difference equals one cup size. Round the band to the nearest even number, then verify the result with a fit check on your body, because no calculator replaces trying the bra on.
What you need before you start
A soft measuring tape gives the most accurate reading, but a piece of string plus a ruler works if you mark the string and measure it flat. Wear an unlined or lightly lined bra rather than a push-up or sports bra, since padded cups change the bust measurement. Stand in front of a mirror so you can keep the tape level all the way around your back.
Measure in inches if you plan to shop US brands, and write both numbers down before you look at any size chart. Taking the measurement twice and averaging the results reduces the chance that a twisted tape or a deep breath throws off your number.
Reading your measurements without overthinking them
Most US brands use the same basic rule: band size comes from your underbust measurement, and cup size comes from the difference between your bust and band measurements. A one-inch difference is typically an A cup, two inches a B, three inches a C, and so on. If your underbust measurement is an odd number, round down to the nearest even number for the band, then adjust the cup if the fit check suggests it.
Size charts vary between brands, so treat your calculated size as a starting point rather than a final answer. If you land between two cup sizes, try both. If you land between two band sizes, start with the larger band and the smaller cup, then sister-size down if the band feels loose.
How cup style changes the size you should try
The same body measurement can translate into different sizes depending on the bra's construction. A full-coverage balconette with side support, like the Entice Lace Full Coverage Side Support Balconette Bra, is designed for fuller cups and provides structure, so your calculated size is usually a reliable starting point. An open balconette neckline, like the Impress Floral Lace Balconette Bra, sits lower on the chest and lifts; the brand's own fit tip notes that if you are fuller on top or between cup sizes, sizing up one cup is worth trying.
Wireless styles behave differently again. The Spellbound Sheer Plunge Wireless Bra uses tringle cups and a wide bottom band for support without an underwire, so the band does more of the work. If your calculated band size feels tight in a wireless bra, that is often a sign to adjust the band rather than the cup.
The fit check that confirms your size
Fasten the bra on the loosest hook and check three things. The band should sit level around your ribcage and stay put when you lift your arms. The center front should rest against your sternum without digging in. The cups should contain your breast tissue without gaping at the top or cutting across the sides.
If the band rides up in the back, it is too loose, so go down a band size and up a cup size. If the cups wrinkle or gap, the cup is too large or the style is too shallow for your shape. If the underwire sits on breast tissue instead of behind it, the cup is too small.
Your at-home fitting steps
- Step 1: Measure your underbust: Wrap a soft tape snugly around your ribcage directly under your bust, keeping it level with the floor. Exhale normally and read the number where the tape meets. Common mistake: pulling the tape so tight it compresses your ribs. It should sit snug, not squeeze.
- Step 2: Measure your bust: Wrap the tape around the fullest part of your bust, usually across the nipple line, without flattening the tissue. Keep the tape parallel to the floor all the way around. Checkpoint: if the tape slopes down in the back, the reading will be too small. Ask someone to check the back line or use a mirror.
- Step 3: Calculate your band size: Use your underbust measurement as your band size. If it is an odd number, round down to the nearest even number for most US brands. Common mistake: rounding up. A band that is one size too large will ride up and stop supporting you.
- Step 4: Calculate your cup size: Subtract your band measurement from your bust measurement. Each inch of difference equals one cup size, starting at A for one inch. Checkpoint: if you are between cup sizes, try both. For open balconette styles, the brand may recommend sizing up one cup when you are fuller on top.
- Step 5: Try the sister size if the band is off: If the band is too tight but the cup fits, go up one band size and down one cup size. If the band is too loose but the cup fits, go down one band size and up one cup size. Common mistake: changing the cup without changing the band. Band and cup sizes move together, not separately.
- Step 6: Do the fit check: Fasten on the loosest hook, then check that the band sits level, the center front touches your sternum, and the cups contain your tissue without gaping or cutting in. Next step: if the fit check fails, adjust one variable at a time and retry before deciding the size is wrong.
Styles worth trying once you know your size
- Entice Lace Full Coverage Side Support Balconette Bra: Full coverage balconette bra with non-padded cups, eyelash-trimmed neckline, and a smoothing back, designed for fuller cups. A structured full-coverage option for anyone whose calculated size lands in the fuller-cup range and who wants side support rather than padding.
- Impress Floral Lace Balconette Bra: Unlined demi lace cups with a hint of show-through and lightweight side slings for side containment; the brand advises sizing up one cup if you are fuller on top or between cup sizes. A good test style if your measurements put you between two cup sizes, since the brand gives explicit guidance on which way to go.
- Spellbound Sheer Plunge Wireless Bra: Wireless plunge bra with tringle cups, a wide bottom band, and stretch mesh backs for added support. Useful if you want a natural shape and a barely-there feel, and a reminder that wireless support comes mostly from the band, so band fit matters more than cup depth.
