Bra Size Calculator
Find your correct bra size using bust and band measurements. Get sizing in US, UK, and EU formats, plus sister sizes for better fit options.
Measure snugly under bust
Measure around fullest part of bust
How do you measure for bra size correctly?
Band size: Measure snugly under bust (directly under breasts) in inches. Round to nearest whole number. If odd, add 1 inch. Example: 33 inches → 34 band. Bust size: Measure around fullest part of bust (usually at nipple level), wearing non-padded bra. Keep tape parallel to ground, not too tight. Example: 38 inches bust. Cup size: Subtract band from bust. Difference determines cup (1"=A, 2"=B, 3"=C, etc.). Example: 38 - 34 = 4" = D cup. Result: 34D. Measure while standing, use soft measuring tape, exhale normally. Remeasure every 6-12 months (weight changes, pregnancy, aging affect size).
What do bra sizes mean and how do they vary by country?
US sizing: Band (inches) + Cup letter. Example: 34C = 34" band, C cup. Cup progression: A, B, C, D, DD/E, DDD/F, G, H, I, J, K. UK sizing: Similar but DD, E, F, FF, G (different progression). EU sizing: Band in cm (70, 75, 80, 85). Cup same letters. Conversion: US 34C = UK 34C = EU 75C. Sister sizes: Same cup volume, different band. 34C = 36B = 32D (go up band, down cup or vice versa). Australian: Similar to UK. Japanese: Uses cm + cup. Brands vary: Always try on, sizes inconsistent across manufacturers. Use conversion charts when buying international.
How do I know if my bra fits properly?
Good fit checklist: Band: Snug, stays level all around (not riding up back), can fit 2 fingers under band comfortably. 80% of support comes from band. Cups: No spillage over top/sides, no gaping/wrinkling, breast fully contained, nipple centered in cup. Straps: Provide 20% support, should not dig in or slip off, adjust to comfortable tension. Gore (center): Lies flat against sternum. Wires: Follow natural breast crease, do not poke/dig. Poor fit signs: Band rides up (too loose), cups overflow (too small), gaping (too large), straps dig in (band too loose), breasts falling out bottom (band too big). Re-fit every 6 months or after weight change 10+ lbs.
Why do bra sizes vary so much between brands?
No industry standard: Each brand uses own patterns, fit models, size charts. Vanity sizing: Brands label larger to make customers feel better (what was 36C is now 34C). Style differences: Push-up adds volume, sports bra fits tighter, balconette vs full coverage different fits. Material: Stretchy vs non-stretch fabrics fit differently. Target market: Brands fit different body types (petite vs plus-size vs athletic). Manufacturing: Tolerance variations in production. Solution: Always try before buying, know your measurements in multiple systems, sister sizes provide options, read reviews for brand-specific fit notes. Professional fitting helps (free at many stores).
What are sister sizes and when should I use them?
Sister sizes have same cup volume but different band/cup combinations. How it works: Increase band by 2", decrease cup by 1 letter (or reverse). Examples: 34C sister sizes: 36B (larger band, smaller cup), 32D (smaller band, larger cup). All have same cup volume. When to use: Current size out of stock, band too tight/loose but cups fit, between sizes. Cup volume stays same: 32D = 34C = 36B = 38A (all have same breast volume). Finding best fit: Try all 3 sister sizes, choose best band fit (should be snug but comfortable). Common switches: 34C too tight → try 36B. 34C band loose → try 32D. Understand: Letter does not mean breast size alone, combined band+cup determines volume.