Measuring the female chest requires two key measurements: one around the ribcage just below the bust, and one around the fullest part of the bust. These two numbers give you everything you need to find your bra size or provide accurate measurements for clothing. The process takes about two minutes with a soft measuring tape.
What You Need Before You Start
Use a flexible fabric or vinyl measuring tape, not a metal one. Wear a non-padded bra that fits reasonably well, or go unlined. Stand in front of a mirror so you can check that the tape stays level all the way around your body. Keep your arms relaxed at your sides except when positioning the tape.
Measuring Your Band Size (Underbust)
Wrap the measuring tape around your ribcage directly beneath your breasts. Pull it snug against your skin so it doesn’t slide down, but not so tight that it digs in or restricts breathing. Make sure the tape is parallel to the floor all the way around, including across your back.
Take a deep exhale before reading the number. You want the smallest measurement your ribcage naturally produces. Round to the nearest whole number. If the number is even, that’s your band size. If it’s odd, round up to the next even number. So a measurement of 33 inches rounds to a band size of 34.
You may encounter older guides that tell you to add four inches to your underbust measurement. This “plus four” method dates back to an era of stiff, non-stretch bra fabrics. Modern bras use elastic materials, so the current global standard is “plus zero,” meaning your underbust measurement (rounded to the nearest even number) is your band size directly.
Measuring Your Bust Size
Wrap the tape around the fullest part of your bust. This is typically at nipple level. Keep the tape straight across your back and parallel to the floor, but hold it loosely. You’re not compressing the tissue here. You want to capture the full circumference without pulling the tape taut. Round to the nearest whole number.
Calculating Your Cup Size
Subtract your band size from your bust measurement. Each inch of difference equals one cup size. Here’s how the math translates in US sizing:
- 1-inch difference: A cup
- 2-inch difference: B cup
- 3-inch difference: C cup
- 4-inch difference: D cup
- 5-inch difference: DD (or E)
- 6-inch difference: DDD (or F)
- 7-inch difference: G
- 8-inch difference: H
So if your band measurement is 34 inches and your bust measurement is 37 inches, the difference is 3, which puts you at a 34C.
Measuring for Clothing Instead of Bras
If you’re measuring for a dress, blazer, or top rather than a bra, the technique is slightly different. Clothing patterns and size charts typically call for a “full chest” measurement. Wrap the tape around your body at the fullest part of your bust, across the nipples, under the armpits, and across the shoulder blades. Keep the tape horizontal and your arms at your sides. Hold it snug enough that it doesn’t slip but loose enough to breathe normally. This single number is what most clothing size charts refer to as “bust” or “chest.”
Tailors and clothing patterns may also ask for a front chest width, which runs across the front of your chest from one armpit to the other without going under the arms. This helps with fitting structured garments like blazers and button-down shirts.
If One Side Is Larger Than the Other
Up to 25% of women have noticeable breast asymmetry, so this is common. When measuring for a bra, take the bust measurement across the fullest part of your larger breast. Fit the bra to the larger side. For the smaller side, you can use a removable pad or bra insert to fill the cup evenly. Some specialty brands make bras designed specifically for asymmetry, with different cup volumes on each side.
Signs Your Measurements Led to the Wrong Size
Numbers are a starting point, not a guarantee. Bra sizing varies between brands, and breast shape affects fit as much as volume does. After trying on a bra in your calculated size, check for these problems:
- Band rides up in back: The band is too loose. Try a smaller band size.
- Breast tissue spills over the top or sides of the cups: The cups are too small. Go up a cup size.
- Cups wrinkle or gap: The cups are too large. Go down a cup size.
- Straps dig into your shoulders: The band isn’t providing enough support, forcing the straps to carry too much weight. A snugger band often fixes this.
- The center panel (gore) doesn’t sit flat against your chest: The cups are too small to contain your breast tissue.
- Underwire pokes or sits on breast tissue: The cup size or shape isn’t right for your body.
A too-tight bra can cause neck pain, numbness in the arms from compression, and chafing or even bleeding around the band. A too-loose bra leads to inadequate support, shoulder grooves from compensating straps, and general discomfort. Neither problem means your measurements were wrong. It often means you need to try a different size within the same range or a different bra style altogether.
International Size Differences
US and UK band sizes both use inches and are often identical. The difference shows up in cup sizing above a D. A US DD is a UK DD, but a US DDD is a UK E, and a US G is a UK F. The numbering diverges further as cup sizes increase.
European (EU) sizing uses centimeters for the band. A 32-inch band converts to a 70 in EU sizing, a 34 converts to 75, and a 36 converts to 80. French sizing adds 15 centimeters to EU band sizes, so an EU 70 becomes a French 85. Cup letters also vary between systems. If you’re shopping internationally, convert your measurements using the brand’s specific size chart rather than assuming your letter carries over.
Sports Bras Use the Same Measurements
Your sports bra size is typically the same as your everyday bra size. Sports bras are designed to fit more snugly for compression and support during movement, but you don’t need to size down. If your calculated size is 34C, start with 34C in a sports bra. It should feel tighter than your regular bra while still allowing you to take a full, comfortable breath.