US Bra Size Calculator
Enter your measurements and get a quick starting size based on standard U.S. bra sizing.
Note: This calculator gives an estimate. Brand sizing, cup shape, and style can change fit.
How this bra size calculator (USA) works
U.S. bra sizing has two parts: a band size (the number) and a cup size (the letter). This calculator uses your ribcage and bust measurements to estimate a practical starting size for shopping in U.S. brands.
1) Band size
The band is calculated from your underbust/ribcage measurement and rounded to the nearest even number (for example, 31.5 becomes 32). In most modern U.S. fitting systems, the band should feel snug and supportive without pain.
2) Cup size
Cup size is based on the difference between your bust measurement and your band measurement. A larger difference means a larger cup letter.
| Difference (inches) | U.S. Cup Size |
|---|---|
| 0 or less | AA |
| 1 | A |
| 2 | B |
| 3 | C |
| 4 | D |
| 5 | DD |
| 6 | DDD/F |
| 7 | G |
| 8 | H |
| 9 | I |
| 10 | J |
How to measure yourself at home
- Wear a non-padded bra (or no bra if preferred) for more accurate tape placement.
- Underbust: Wrap tape around your ribcage directly under your breasts. Keep it level and snug.
- Bust: Measure around the fullest part of your bust with tape parallel to the floor.
- Stay neutral: Relax shoulders and breathe normally; don’t over-tighten the tape.
- Repeat: Measure 2–3 times and use the average.
Understanding sister sizes (very useful in U.S. stores)
If your calculated size is close but not perfect, try a sister size:
- Go down one band (e.g., 34 to 32) and up one cup (C to D).
- Go up one band (e.g., 34 to 36) and down one cup (C to B).
Example: 34C has sister sizes 32D and 36B. Cup volume stays close while band fit changes.
Common fit issues and quick fixes
Band rides up in back
Usually means the band is too loose. Try one band size smaller (and one cup size larger to keep volume similar).
Cups gape at top
Could mean cups are too large, style mismatch for your shape, or straps are too loose. Try adjusting straps or a different cup/style.
Spillage over cup edge
Often indicates cups are too small. Try increasing cup size first.
Underwire pokes sides
Try a larger cup or a style with wider wires; some brands run narrow or wide in the cup.
FAQ: bra size calculator USA
Is this calculator 100% accurate?
No calculator is perfect. Think of it as a strong starting point, then fine-tune based on fit and comfort.
Do all U.S. brands size the same way?
Not exactly. Some use DD, DDD/F, then G/H; others label cups differently. Always check the brand chart.
Should I measure in inches or centimeters?
Either one works here. The calculator converts centimeters to inches automatically before estimating your U.S. size.
How often should I re-measure?
Every 6–12 months, or sooner after significant body changes, pregnancy/postpartum changes, or weight fluctuations.
A good bra should feel supportive, stable, and comfortable all day. Use the calculator result, try nearby sizes, and prioritize fit over label.