Bra Size Calculator
Enter your measurements to get a starting bra size. For best results, measure without a padded bra and keep the tape level around your body.
Why measurements matter for bra fit
A bra calculator is only as good as the measurements you enter. If your tape is tilted, too loose, or placed over bulky clothing, the result can be off by one or even two cup volumes. That usually leads to common fit issues: slipping straps, band riding up, cup gaping, or spillage.
The goal is not to find a perfect final size in one step. The goal is to find a strong starting size you can fine-tune by brand, style, and comfort preference.
What you need before measuring
- A soft measuring tape (sewing tape works best).
- A mirror to keep the tape level front to back.
- Light clothing or no bra, if comfortable.
- A few minutes to repeat each measurement once for accuracy.
How to measure for a bra calculator (step by step)
1) Snug underbust
Wrap the tape directly under your breasts where the bra band sits. Keep it parallel to the floor and pull snugly. You should feel firm contact but still be able to breathe comfortably.
2) Standing bust
Stand naturally and measure around the fullest part of your bust. Avoid pulling the tape tight; it should just rest against the skin.
3) Leaning bust
Lean forward so your torso is roughly parallel to the floor. Measure around the fullest tissue. This helps capture breast volume that may not be fully represented in the standing measurement.
4) Lying bust
Lie on your back and measure again at the fullest point. This balances the standing and leaning readings and helps calculators estimate volume more consistently.
How the calculator turns measurements into size
Most calculators estimate:
- Band size from your snug underbust (rounded to the nearest even number).
- Cup size from the difference between your bust average and the estimated band.
If the result is 34D, for example, that means a band around 34 and a cup volume associated with that band. Cup letters are relative to band size, so a 34D and 36C can have similar cup volume (these are called sister sizes).
Common measuring mistakes
- Measuring over thick shirts or padded bras.
- Letting the tape angle upward on your back.
- Holding your breath or inflating your chest.
- Using only one bust measurement instead of multiple positions.
- Assuming one brand's fit applies to all brands.
After you get your result
Use your calculated size as a starting point. Try nearby sister sizes if needed:
- If the band feels too tight but cups are good, go up one band and down one cup letter.
- If the band feels too loose but cups are good, go down one band and up one cup letter.
- If cups cut in at the top or sides, try a larger cup.
- If cups wrinkle or gap significantly, try a smaller cup or different cup shape.
Quick fit checklist
- Band sits level and stays in place on the loosest hook when new.
- Center gore (front panel) rests close to your sternum in wired bras.
- No major spillage, pinching, or empty cup space.
- Straps support lightly without digging into shoulders.
Final note
Bra fitting is both measurement and preference. Your calculator result gives you a data-driven baseline, but comfort and support are personal. Use the number as a guide, then adjust until the fit feels secure, smooth, and easy to wear all day.