Find your perfect sports bra fit by entering three simple measurements. Input your above bust (chest), bust (fullest part), and below bust (rib cage) measurements in inches, and the Sports Bra Size Calculator returns your recommended band size and cup size — so you can shop with confidence and get the support you need for any activity.
Recommended Bra Size
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Band Size
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Cup Size
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Cup Difference (inches)
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Sister Size Down
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Sister Size Up
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To calculate your bra size, you need two numbers: your band size and your cup size. Your band size is determined by your rib cage (below bust) measurement, rounded to the nearest even number. Your cup size is found by subtracting your band size from your bust measurement — each inch of difference corresponds to one cup size (1" = A, 2" = B, 3" = C, etc.).
Your band size is based on your rib cage measurement taken just below your breasts. Round this measurement to the nearest even number. If the result is odd, round up to the next even number. For example, a 31" rib cage measurement rounds to a 32 band.
Cup size is the difference in inches between your bust measurement and your band size. A 1-inch difference = A cup, 2 inches = B cup, 3 inches = C cup, 4 inches = D cup, 5 inches = DD (or E), 6 inches = DDD (or F), and so on.
Yes — DDD and F refer to the same cup size. Different brands use different naming conventions. US brands commonly label this size DDD, while UK and many European brands call it F. When shopping internationally or across brands, it helps to know both equivalents.
The +4 method is an older sizing technique where 4 inches were added to the rib cage measurement to determine the band size. This was developed when bra materials were less stretchy. Modern bras use more elastic fabrics, so most current sizing guides — including this calculator — use the actual rib cage measurement rounded to the nearest even number for a more accurate fit.
It depends on the issue. If the band feels too tight but the cup fits, try a larger band size and go down a cup (a sister size). If the cups overflow but the band fits, go up a cup size. A well-fitting bra should have the band sitting level across your back, providing about 80% of your support.
For the most accurate measurements, wear a non-padded, well-fitting everyday bra or a shelf-bra camisole. Avoid push-up bras or heavily padded styles, as these can add volume and skew your bust measurement. Stand straight, breathe out normally, and keep the tape measure snug but not compressing.
The underlying band and cup measurements are calculated the same way for both sports bras and regular bras. However, sports bras often run slightly smaller due to firmer, compression-style construction. If you're between sizes or new to a brand, consider sizing up one band size for a more comfortable athletic fit, especially for high-impact activities.