Bra Size Calculator (US Sizing)
Enter your measurements to get a quick starting size. You only need two numbers: snug underbust and full bust.
Note: This is an estimate. Brand cuts, breast shape, and personal comfort can shift your best fit.
How this bra size calculator works
The calculator uses a common modern method: it rounds your snug underbust to the nearest even band size, then compares your full bust measurement to that band size to estimate cup volume. The difference between those two values determines the cup letter.
- Band size: based on underbust, rounded to the nearest even number.
- Cup size: based on bust minus band difference in inches.
- Output: estimated US size (for example, 34C, 36DD/E).
Step-by-step measuring guide
1) Measure your underbust
Wrap the tape around your ribcage directly under your bust. Keep it level and snug, not loose. Exhale normally and record the number.
2) Measure your full bust
Measure around the fullest part of your bust. Keep the tape parallel to the floor and avoid pulling too tight. Record this number as well.
3) Enter values and calculate
Select inches or centimeters, enter both numbers, and click Calculate size. If you use centimeters, the tool automatically converts to inches before estimating your size.
Understanding your result
Your final size has two parts:
- Band number (like 32, 34, 36): how the bra fits around your ribcage.
- Cup letter (like B, C, D, DD): bust volume relative to the band.
Cup letters are not absolute. A 32D and a 36D do not have the same cup volume. Cup size changes with band size. That is why sister sizes can be helpful when fit is close but not perfect.
Common fit checks after calculating
- Band rides up in back: try a smaller band (or tighten hooks).
- Band feels painfully tight: try one band up, then adjust cup as needed.
- Cups gap at top: try a smaller cup, different cup shape, or both.
- Spillage over cup edge: try a larger cup.
- Center gore does not tack: often a sign the cup is too small or shape mismatch.
Why your size may vary by brand
Even with a strong measurement-based starting point, sizing can vary across brands and styles. Balconette, plunge, full-coverage, and sports bras all fit differently. Fabric stretch, wire shape, and cup height can all change how a bra feels.
Treat this calculator as your first draft, then refine by trying nearby sizes (especially sister sizes) to find your best everyday fit.
Quick FAQ
Is this calculator accurate?
It is accurate as a starting estimate. Final fit still depends on shape, brand, and style.
Can I use centimeters?
Yes. Choose centimeters in the dropdown and enter your measurements directly.
What if Iām between sizes?
Try the nearest size plus one sister size up and down to compare comfort and support.