Bra Size Calculator
Calculate your bra band size and cup size from underbust and bust measurements.
Results
What is it?
The Bra Size Calculator estimates your US band size and cup size from two body measurements: underbust circumference (for the band) and fullest bust circumference (for the cup). Band sizes are even numbers (28–42+); cup sizes are lettered (A=1", B=2", C=3", D=4", DD/E=5", DDD/F=6").
How to use
Measure your underbust (just below the breasts, snug but not tight) and your bust (around the fullest part of the chest, keeping the tape horizontal). Enter both measurements in inches. The calculator outputs your band size and the inch difference to map to your cup letter.
Example scenario
Underbust = 32", Bust = 36". Band size rounds to 32. Difference = 36 – 32 = 4 inches maps to Cup D. Final size: 32D.
Pro tip
Sister sizing lets you go up or down a band size while maintaining the same cup volume: a 32D equals a 34C and a 30DD. If a bra fits the cups but the band is uncomfortable, try a sister size. For the most accurate result, always get professionally fitted at a lingerie store — measurements can vary by brand and bra style.