bra size calculator
Stop guessing your bra size. Use our free breast size calculator and discover the perfect fit for comfort, confidence, and support
Putting on the correct bra size can transform your comfort, posture, and confidence. Yet, its been said that a lot of women are unknowingly wearing the wrong type and size of bra. I created this tool to help solve this problem. My calculator simply take two quick measurements and lets you get the accurate size — no confusion, no guesswork. It give you the results in US, UK, EU, FR/BE/ES, AU & NZ sizes
How It Works
Finding your true bra size is easier than you think:
Step 1: Measure your bust and band using a tape measure.
Step 2: Enter your measurements into our calculator.
Step 3: Instantly discover your correct bra size along with personalized tips for the perfect fit.
No complicated charts. No confusing sizing guides. Just quick, accurate results.
Why Proper Size
Wearing the correct size isn’t just about looks — it’s about comfort and health.
✅ Better Comfort: No more slipping straps or tight bands.
✅ Improved Posture: Proper support reduces back and shoulder strain.
✅ Confidence Boost: Clothes fit better and you feel amazing.
✅ Longevity: A well-fitted bra lasts longer and stays in shape.
How we computed this
• Cup size is determined by the difference between bust and band measurements in inches (for example: 1″ = A, 2″ = B, 3″ = C, etc.).
• For US/UK/AU/NZ we use a rounded even band number typical for those markets. For EU we round the band in cm to the nearest 5 (70,75,80…).
• French/Belgian/Spanish band numbers are shown as the common French system (EU band + 15).
Note: bra sizing varies by brand and style; the calculator gives standard conversions to guide you
FAQs
Many calculators ask for two basic measurements — a snug under-bust (band) measurement and a full bust measurement — then from those 2 measurements compute the numerical band and the difference between bust and band to assign a cup letter (that difference-to-cup mapping is how many calculators work).
Some calculators also ask about shape, weight changes, pregnancy, or preferred fit to refine results. Keep in mind calculators give a starting point — they estimate volume from simple inputs and can’t fully account for breast shape, fabric stretch, or brand differences
Wear a non-padded bra (or no bra) and stand relaxed. Measure under the breasts with the tape snug and parallel to the floor for the band.
Measure across the fullest part of the bust (again parallel to the floor) without squashing the breasts. Record measurements to the nearest quarter-inch or nearest centimeter, repeat once or twice, and use the average.
Enter those numbers into the calculator and try the suggested size plus the immediate sister sizes when you shop. (Retail fitting guides give detailed step-by-step instructions.)
Sizing isn’t standardized across the industry. Brands use different sizing systems (US vs UK vs EU), cut fabrics differently, and build cups/bands with different stretch and structure, so the same labeled size can fit differently across brands.
Calculators also implement slightly different mapping rules or rounding conventions. Finally, breast shape (full-on-top vs full-on-bottom, wide vs close set) changes how a given size actually fits.
That’s why the calculator result is a starting recommendation — trying on multiple sizes/styles is essential
“Sister sizes” are sizes with the same cup volume but different band/cup labels.
A simple rule: if you go down one band size (e.g., 34 → 32), go up one cup letter (C → D) to keep the same cup volume; if you go up one band (34 → 36), go down one cup letter (C → B). Example: 34C’s sisters include 32D and 36B.
Try sister sizes when the band feels too tight/loose but the cup seems right, or when you can’t find your exact labeled size in a style you like
Look for these signs of good fit: the band is level and snug (the band should provide most support and sit on the loosest hook when new); cups fully contain the breast with no spillage or gaping; underwire lies flat around the breast tissue without poking; center gore (bridge) sits flat on the sternum; straps don’t carry the bulk of the weight (they should be adjusted for comfort, not to hold the bra up).
If any of these fail, try the sister sizes or a different style. Professional fitters or multi-brand try-ons are the best way to confirm final fit
