Bra Size Calculator

About the Bra Size Calculator

Estimates bra band and cup size from your underbust (band) and bust measurements in inches, using the common US sizing method. Fit varies by brand, treat this as a starting point.

How to use

Enter your underbust and bust measurements in inches, then click Calculate.

Worked example

Band 32 in, bust 35 in → about 32C.

How to use this calculator

1. Measure your band around the ribcage, directly under the bust, using a snug tape.
2. Measure your bust around the fullest part of the chest, keeping the tape level.
3. Subtract the band measurement from the bust measurement to estimate the cup difference and use the calculator's sizing guide to convert that difference into a bra size.

The formula explained

• \(\text{band}\) = Measured underbust or ribcage measurement used for the band size
• \(\text{bust}\) = Measured around the fullest part of the bust
• \(\text{cup}\) = The difference between bust and band that is mapped to a cup letter

Step by step method

1. Record your band measurement in the same units as your bust measurement.
2. Record your bust measurement at the fullest point, without compressing the breasts.
3. Find the difference by subtracting band from bust.
4. Use the result with the tool's bra size guide to estimate the size.

Worked example

For example, if someone measures a 34 inch band and a 37 inch bust, the calculator uses the difference to estimate the cup size.

1. Band = 34 and bust = 37, so \(\text{cup} = 37 - 34\).
2. That gives \(\text{cup} = 3\).
3. A 3 inch difference is typically mapped to a C cup in standard sizing guides.

Tips and common mistakes

• Keep the measuring tape level and snug, but not tight.
• Use the same unit for both measurements, such as inches or centimeters.
• If you are between sizes, try nearby band and cup combinations because fit can vary by brand.
• A bra size estimate is only a starting point, so checking the fit in the cup, band, and straps matters.

Frequently asked questions