Sports Bra Sizing Guide: Measuring at Home in 5 Minutes

Here's the quick version: wrap a soft tape snugly around your ribcage directly under your bust for the band measurement, then around the fullest part of your bust for the bust measurement. The difference between those two numbers in inches roughly maps to a cup size (a 1-inch difference is about an A, 2 inches a B, 3 inches a C, and so on), while the band number itself maps to your band size. Round the band measurement to the nearest whole number, and you have a starting size in under five minutes.

What You Need Before You Start

Grab a soft fabric measuring tape (not a rigid one), wear a well-fitting, unpadded bra or go without one, and stand in front of a mirror if you can. Measuring over a heavily padded bra or loose top will throw off both numbers, so strip down to skin or a thin, close-fitting layer for accuracy.

Step 1: Measure the Band

Wrap the tape directly under your bust, around your ribcage, keeping it level and parallel to the floor all the way around your back. It should sit snug enough that you feel it, but not so tight it compresses your ribs - snug like a good sports bra band should ultimately feel. Round to the nearest whole inch; this is your band size number.

Step 2: Measure the Bust

With the tape still level, measure around the fullest part of your bust, usually across the nipple line, keeping the tape snug but not compressing. Don't lean forward or pull the tape tight enough to flatten anything - you want the natural fullest circumference.

Step 3: Calculate the Difference

Subtract the band measurement from the bust measurement. That difference in inches corresponds to a rough cup size: 1 inch is typically an A cup, 2 inches a B, 3 inches a C, 4 inches a D, and so on up the alphabet. This isn't a perfect science across every brand, but it gets you within one size of correct almost every time, which is a solid starting point for online ordering.

Applying Your Measurements to Sports Bra Styles

Once you have a band and cup estimate, match it to the support style you need. Close-fitting, medium-support pieces like the Women's Tight Cropped Sports Bra (80% nylon, 20% spandex, 220 g/m²) run true to a snug fit at your calculated size, while looser cropped styles like the Women's Halter Neck Yoga Sports Bra (78% polyamide, 22% elastane, 220 g/m²) may feel slightly more relaxed at the same numbers because of the halter cut. If your measurements land between two sizes, size down for a compressive, high-impact style and size up for comfort-first, low-impact wear.

When to Re-Measure

Re-measure every six months or after any significant weight change, since band and bust measurements shift more than people expect. Elastic in older bras also stretches out over time, which can make you think you've changed size when it's really the garment relaxing - re-measuring with a fresh tape check settles that question quickly. Styles like the Women's Color Block Ruched V-Neck Sports Bra (75% nylon, 25% spandex, 230 g/m²) use ruching at the center front, which can mask minor sizing shifts visually, so rely on the tape measurement over how a bra looks in the mirror.

Common Measuring Mistakes

The most common error is measuring over a padded or ill-fitting bra, which inflates the bust number. The second is pulling the tape too tight on the band, which makes you size down into something that will feel restrictive during actual training. The third is measuring bust with shoulders hunched or arms raised, which distorts the fullest-point number - stand naturally, arms relaxed at your sides.

Bust Minus Band	Approximate Cup
1 inch	A
2 inches	B
3 inches	C
4 inches	D
5 inches	DD/E

FAQ

Should I measure myself in the morning or evening?

It doesn't significantly matter for sports bra sizing, but measure at a consistent time if you're comparing against a previous measurement, since minor bloating or fluid shifts can move the bust number slightly.

How often should I re-measure for a sports bra?

Every six months or after any noticeable weight change - band and bust measurements shift more than most people expect, and re-measuring takes less time than dealing with an ill-fitting bra.

What is the difference between UK/US and EU sports bra sizing?

US and UK sizing typically use the same band-plus-letter system (like 34B), while EU sizing uses a different band number scale entirely - always check a brand's specific size chart rather than assuming direct conversion.

Does the bust-minus-band method work for every cup size?

It's a reliable starting estimate across most sizes, but very large or very small differences can fall outside the standard letter progression - if your calculated size feels off in practice, size up or down by one and reassess using the 5-point fit check.

Related reading: how leggings should fit, legging length guide, and how many workout outfits you actually need. Shop sports bras in tops.