Bra Size Calculator
Calculate bra size with personalized inputs and reference ranges for healthy values.
How to Find Your Bra Size
A properly fitting bra starts with two measurements: your band size (the circumference of your ribcage just under your bust) and your bust size (the circumference at the fullest point of your chest). The band number comes from rounding your underbust measurement to the nearest even number. The cup letter is determined by the difference between your bust and band measurements – each inch of difference represents one cup size. This calculator converts your measurements into your recommended bra size across US, UK, and EU sizing systems.
How to Measure Correctly
Use a soft measuring tape and wear a non-padded bra or no bra. For the band measurement, wrap the tape snugly around your ribcage directly under your bust, keeping it level and parallel to the floor. For the bust measurement, wrap the tape around the fullest part of your chest without compressing the tissue. Keep the tape level and breathe normally. If the band measurement is odd, round up to the next even number. A 1-inch difference between bust and band is an A cup, 2 inches is B, 3 inches is C, 4 inches is D, and so on.
Sister Sizes and Fit Adjustments
If your calculated size does not feel right, sister sizing can help. Sister sizes share the same cup volume but with a different band. For example, 34C, 32D, and 36B all have the same cup volume. If a 34C band feels too tight, try 36B. If it feels too loose, try 32D. The cup volume stays consistent while the band adjusts to your comfort preference. About 80% of bra fit issues come from the band being too loose – a well-fitting band should feel snug and level across your back without riding up.
Signs of a Poor Fit
The band rides up in the back (band too loose). Straps dig into shoulders (band not providing enough support, forcing straps to compensate). Cups overflow or gap at the top (wrong cup size). The center gore does not sit flat against your sternum (cups too small). Underwire sits on breast tissue instead of the ribcage (cup too small or wrong shape). An estimated 70–80% of women wear the wrong bra size, most commonly a band too large and a cup too small.
Frequently asked questions
How do I measure my bra size at home?
What is a sister size?
Why does my bra size vary between brands?
How often should I get remeasured?
What is the most common bra fitting mistake?
Does bra size affect back pain?
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