Free bra size calculator
Calculate your band and cup size from two measurements: underbust and bust. Use inches or centimeters and choose your sizing region.
Bra size calculator
Use inches or centimeters and get US, UK, EU, French, and AU/NZ size results with sister-size guidance.
You need two measurements:
Measure around your ribcage directly under your bust. Keep the tape level and snug.
Measure around the fullest part of your bust. Keep the tape straight and relaxed.
Tip: Use a soft measuring tape and measure without thick clothing or padding.
Bra sizing is not perfectly standardized across brands. Your result gives you a measurement-based starting point, then you can adjust using fit checks, sister sizes, and brand size charts.
Measurement guide
Use these quick steps before entering your underbust and bust measurements.
Wrap the tape snugly around your ribcage, directly under your bust. Keep it level across your back.
Measure around the fullest part of your bust. Keep the tape relaxed, straight, and comfortable.
Enter both measurements in the same unit, choose inches or centimeters, and select your sizing region for a starting size.
Need more detail? Read the full guide on how to measure bra size.
This calculator estimates your bra size from two measurements:
The difference between your bust and band measurements helps determine the cup letter. Your selected country changes the size label because US, UK, EU, French, and AU/NZ systems use different band and cup naming rules.
| Bust measurement | Difference | Starting size |
|---|---|---|
| 33 in / 83.82 cm | 1 inch | 32A |
| 34 in / 86.36 cm | 2 inches | 32B |
| 35 in / 88.90 cm | 3 inches | 32C |
| 36 in / 91.44 cm | 4 inches | 32D |
These examples use a 32-inch (81.28 cm) underbust and whole-inch cup differences. Half-inch boundaries, breast shape, and differences between brands can change which nearby size fits best. Cup letters above D follow different US and UK sequences; this table is a calculation example, not a guarantee of fit.
Use the six-measurement calculator for more measurement context, then check band comfort, cup coverage, and wire placement when trying a bra. See our method and editorial policy or report a problem.
Bust size is a measurement around the fullest part of your chest; bra size combines a band and a cup. A bust measurement alone does not determine a bra size. For example, a 36-inch bust paired with a 32-inch band gives a four-inch difference (32D). Paired with a 34-inch band, the same bust measurement gives a two-inch difference (34B). These are examples of the sizing calculation, not exact measurements for everyone who wears those labels. Measure your underbust as well as your bust before choosing a size.
Wacoal's sizing explanation illustrates the band-and-cup calculation. Different fitting methods and brands can produce different starting sizes; use the cup measuring guide and the retailer's own chart to compare them.
For more examples, see the bra size calculator in inches or our guide to bra size, bust and band measurements.
Choose the system used by the bra brand you are shopping for. The measurement unit and sizing system are separate: you can enter centimeters and still calculate a US or UK bra size.
Already know a size that fits? Use the bra size converter to compare international labels, or the sister size calculator to adjust the band while keeping a similar cup volume. Brand charts take priority when their labels differ.
Understand the result
A bra size combines a band number and a cup letter.
For example, in 34C:
Cup letters are not fixed volumes by themselves. A 34C and 36C do not have the exact same cup volume because cup size changes with band size.
Fit check
The band should feel snug and stay level around your body.
The cup should contain breast tissue without gaping, spilling, or cutting in.
The center gore and underwire should sit comfortably without pressing on breast tissue.
Troubleshooting
Your result is a starting point. If the first size does not feel right, use these checks:
Try a smaller band size, or a sister size with a smaller band and larger cup.
Try a larger cup size, or check whether the cup shape is too shallow.
Try a smaller cup, a different cup shape, or a sister size depending on how the band feels.
The band may be too loose, causing the straps to carry too much weight.
Try a larger cup, a wider wire, or a cup shape with more room where your tissue sits.
More detail
The standard calculator uses two measurements: underbust and bust. That works well for a quick starting size.
The advanced bra size calculator uses six measurements to better account for breast projection, fullness, tissue distribution, and measurement variation.
No. Bust size is the circumference around the fullest part of your chest. A bra size combines a band number and a cup letter. A 36-inch bust alone cannot tell you your bra size: you also need your underbust measurement and the sizing system. Enter both measurements above to get a starting estimate.
Measure your underbust directly under your bust, then measure around the fullest part of your bust. Enter both measurements into the bra size calculator, choose inches or centimeters, and select your sizing region to estimate your starting band and cup size.
The calculator gives a measurement-based starting size, not a guaranteed final fit. Bra fit can still change by brand, fabric, wire width, cup shape, and personal comfort.
Use whichever unit is easiest for you. The bra size calculator works in inches and centimeters, as long as you use the same unit for both underbust and bust measurements.
US and UK bra sizing use different cup-label progressions, especially after D. Your body measurements can be the same while the displayed size label changes by region or brand.
No. Enter your actual snug underbust measurement. This calculator rounds to a band size without adding four inches. Some retailers use a different fitting method, so compare their size chart and check the fit before buying.
Sister sizes are nearby sizes with similar cup volume but different band sizes. For example, if the cups feel close but the band is too loose, a smaller-band sister size can help.
Start with the size closest to your measurements, then compare the fit. If the band feels wrong but the cups are close, use sister sizing; if the cups spill or gape, adjust cup size or cup shape.
Yes. The calculator uses the difference between bust and band measurements to estimate cup size, then combines that cup estimate with your band size and selected sizing region.
Related tools
Use six measurements for a more detailed fit check when the standard result feels close but not quite right.
Open Advanced bra size calculatorFind nearby sizes when your cup volume feels close but the band needs adjusting.
Open Sister size calculatorCompare band and cup labels across common sizing systems before shopping.
Open Bra size chartConvert sizes between US, UK, EU, French, and AU/NZ labels.
Open Bra size converterLearn what band numbers and cup letters mean in real fit terms.
Open Bra size meaningsFollow the full measuring tutorial if you want more detail before using the calculator.
Open How to measure bra sizeUse an inches-focused calculator page when you prefer US-style measurements.
Open Bra size calculator in inches