Skip to main content
Calculator Answers

Bra Size Calculator

Blake Boege
Written by Blake Boege · Founder, Calculator Answers

A bra size calculator is a fitting utility designed to estimate a person's correct brassiere size using physical body measurements. The sizing system consists of a band size (computed by adjusting the underbust circumference to an even number) and a cup size (determined by the difference between the fullest part of the bust and the band size). Standard US sizing maps each inch of difference to alphabetical cups, starting with AA for zero difference. Women use this calculator to find a comfortable starting size, though actual fit varies by brand, style, and breast shape.

Enter your underbust and fullest bust measurements in inches to calculate your estimated band size, cup size, and recommended bra size.

See also: Body Fat Calculator, Waist to Hip Ratio Calculator, and BMI Calculator.

Quick Answer

Calculate your estimated bra band and cup size. Enter your underbust (band) and bust measurements to find your US/UK size.

Measurements

in

Snug measurement directly under your bust. · e.g. 32

in

Loose measurement around the fullest part of your chest. · e.g. 35

How to Measure Tips

  • Keep the tape parallel to the floor all the way around.
  • Stand relaxed and exhale naturally when taking measurements.
  • Use a flexible measuring tape for accuracy.
Recommended Size

Recommended Bra Size

32C

Band: 32 · Cup: C

Band Size32 in
Cup SizeC
Bust-to-Band Difference+3 in

Approximate size only — brands and bra styles vary. If the calculated band feels snug, try its sister size (e.g. try a 34B if 32C is too tight).

Was this helpful?

Examples

Underbust: 32″ · Bust: 35″

Recommended: 32C · Band: 32 · Cup: C

Underbust: 33″ · Bust: 36″

Recommended: 34B · Band: 34 · Cup: B (odd rounded up)

Underbust: 29.5″ · Bust: 35″

Recommended: 30DD/E · Band: 30 · Cup: DD/E

Underbust: 38″ · Bust: 39″

Recommended: 38A · Band: 38 · Cup: A

How it works

Sizing Calculations & Logic

This calculator estimates bra sizing using the standard US system:

1. Band Size:

We round the underbust measurement to the nearest whole inch. If the rounded value is even, that is your band size. If it is odd, it is rounded up to the next even number:

Band = rounded underbust is even ? underbust : underbust + 1

2. Cup Size:

We calculate the difference between your fullest bust measurement and your calculated band size:

Difference = bust − band size

The difference is mapped to the standard US cup size progression:

  • 0″ or less = AA
  • 1″ = A
  • 2″ = B
  • 3″ = C
  • 4″ = D
  • 5″ = DD / E
  • 6″ = DDD / F
  • 7″ = G
  • 8″ = H

How to get the best fit

Measure wearing a thin, unpadded bra or no bra. Stand straight and keep your breathing natural. If your calculated size feels tight in the band, try a "sister size": go up one band size and down one cup size (for example, if you calculated a 34C, your sister size is 36B).

Note: Bra sizes are approximate. Band elasticity, wire curvature, and cup shapes differ across makers and styles. Use this calculated size as a guide to begin fitting.

Related Calculators

More tools from Health

Body Fat CalculatorEstimate body fat percentage using the U.S. Navy circumference method, with the standard fitness category scale.Waist to Hip Ratio CalculatorCalculate waist-to-hip ratio (WHR) from waist and hip measurements taken at the landmarks WHO specifies. Returns the ratio, and shows where WHO's published cut-off for substantially increased risk falls.BMI CalculatorCompute Body Mass Index from height and weight, with the standard category scale and the healthy weight range for your height.Body Shape CalculatorEnter bust, waist and hip measurements and see which of five categories they fall into under this page's own cut-offs: hourglass, rectangle, pear, apple, or inverted triangle.

Frequently asked questions

Exhale fully and wrap a soft measuring tape snugly around your ribcage directly beneath your breasts. Keep the tape parallel to the floor. Round the measurement to the nearest inch.

Stand straight, wearing a thin unpadded bra or none at all. Do not measure over a padded or lined bra. The cup letter comes from the bust measurement minus the band measurement rounded to the nearest inch, so one inch of foam is one whole cup letter, and the same body can come out a B or a C depending on what it was wearing. Wrap the tape around the fullest part of your bust, level all the way round. Do not pull the tape tight; it should rest gently against your skin.

Traditionally, standard bra band sizing uses even numbers. If your raw measurement is an odd number (like 33 inches), standard sizing rules suggest rounding up to the next even number (34) or adding 1 inch to find a comfortable fit.

Cup size is determined by the difference between your fullest bust measurement and your band size. Each inch of difference corresponds to a letter: 1 inch = A, 2 inches = B, 3 inches = C, 4 inches = D, etc. If the difference is zero or negative, the size is AA.

Bra manufacturing patterns, elasticity of fabrics, and wire styles vary significantly between brands and designs. A calculated size is only a baseline; you should always try on sister sizes (e.g. going up a band and down a cup) to find the best fit.