Measure your underbust
Wrap the tape snugly around your ribcage, directly under your bust. Keep it level across your back.
Find your bra size
Two measurements. A starting size for your fit.
Measuring guide
How to measure
For the most accurate fit, wear a non-padded bra and stand naturally.
1
Underbust
Snug around your ribcage, below your bust.
2
Bust
Around the fullest part, without pulling tight.
Want a more detailed estimate? Use 6 measurements
Need help with your measurements or result? Start here.
01 / Measure
How to measure your bra size
Use a soft measuring tape and take both measurements in the same unit. Keep the tape level and avoid thick clothing or padding.
Measure your bust
Measure around the fullest part of your bust. Keep the tape relaxed, straight, and comfortable.
Calculate your size
Enter both measurements in the same unit, choose inches or centimeters, and select your sizing region for a starting size.
02 / Understand
How this bra size calculator works
Your underbust measurement helps determine the band. The difference between bust and band helps estimate the cup, and your sizing system determines the label.
Start with your actual measurements
For an inch-based band, this tool rounds your underbust to a whole inch, then up to an even band number if needed. Enter your measured underbust without adding four inches.
A worked example · US / UK
36Bust (in)32Band (in)4Difference
Starting size 32D
The number is your band; the letter is your cup. Cup letters are relative to the band, so 32D and 34D have different cup volumes.
Bust size isn’t bra size. Bust circumference alone cannot determine a bra size. A bust size calculator also needs your underbust measurement.
| Bust | Difference | US / UK |
|---|---|---|
| 33 in83.82 cm | 1 inch | 32A |
| 34 in86.36 cm | 2 inches | 32B |
| 35 in88.90 cm | 3 inches | 32C |
| 36 in91.44 cm | 4 inches | 32D |
These examples use a 32-inch (81.28 cm) underbust. Rounding boundaries can affect nearby results. US and UK cup labels differ above D; fit also varies by brand and shape.
More examples in inches03 / Check the fit
Check how your bra fits
A calculated size is a starting point. When you try a bra, check comfort and support as well as the label.
A level, secure band
It feels snug without digging in and stays in place when you move.
Cups that contain comfortably
Breast tissue sits inside the cups without spilling or a cutting edge.
Comfortable wires and center
In wired bras, wires surround the tissue. The center should rest comfortably; its position varies with construction.
- Band rides up
- Check band tension. If the cups fit, a smaller-band sister size may help.
- Cups spill over
- Check cup size and depth. A larger cup or a different shape may give more room.
- Cups gape
- Check strap adjustment and cup shape before assuming you need a smaller cup.
- Straps dig in
- Loosen overtightened straps and check whether the band is providing enough support.
- Wire presses on tissue
- Check wire width and cup room. Size or shape may need adjusting.
04 / Compare systems
US, UK and international bra sizes
Choose the system used by your brand. Units and sizing systems are separate: you can measure in centimeters and still calculate a US or UK size.
US and UK band numbers match, but cup labels differ after D. EU, French, and AU/NZ systems use different band labels. Always check the brand’s own chart.
- United StatesUS size chart
- United KingdomUK size chart
- EuropeEU size chart
- FranceFrench size chart
- Australia / New ZealandAU / NZ size chart
Already know a size that fits? Use the bra size converter to compare international labels. For measurements in the UK system, use the UK bra size calculator.
Browse all bra size charts05 / Common questions
Common bra sizing questions
Is bust size the same as bra size?
No. Bust size is the circumference around the fullest part of your chest. A bra size combines a band number and a cup letter. You need both bust and underbust measurements, plus a sizing system, to estimate a starting size.
How accurate is a bra size calculator?
It gives a measurement-based starting size, not a guaranteed fit. Brands, fabrics, wire widths, cup shapes, and personal comfort can change what works for you. Try the suggested size and check how the band and cups fit.
See how a bra should fitDo I add four inches to my underbust?
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 chart and check the fit before buying.
Should I measure with a bra on?
If you wear one, choose a thin, non-padded bra that holds your bust naturally. Avoid padding, push-up styles, or compression that changes the measurement. Measuring without a bra is also an option; follow the instructions for the calculator you use.
Read the guide to measuring with a braWhat should I do if I am between sizes?
Compare nearby sizes and check the band and cups separately. If the cups feel right but the band needs adjusting, try a sister size. Gaping or spilling can also come from a cup-shape mismatch, so a different style may help.
Find your sister sizesWhen should I use the six-measurement calculator?
Use it when the quick estimate feels close but inconsistent, or you want to include more measurement positions. The extra measurements provide more context for your starting size. You still need to check the fit of the actual bra.
Use the advanced bra size calculator06 / Our approach
About our sizing guidance
Published by Bra Size Calculator. Our tools turn measurements into a starting size and provide practical fit guidance. They do not replace a professional fitting or clinical advice.
Calculator outputs are not sponsored placements. Affiliate links may support the site, but they do not determine sizing guidance. Read our method and editorial policy or report a correction.
Content updated . A content update does not indicate a professional or medical review.