Calculator
Bra Size Calculator
Enter underbust and bust measurements, switch between inches and centimetres, and get an instant US starting size.
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34D
Calculator
Get your bra size in 30 seconds
USUKEUFRAU
Bra sizing tools
Find a bra size that finally makes sense.
Calculate your size, convert between US, UK, EU, French and Australian systems, and discover sister sizes — all in one place.
36common sizes
5size systems
No account needed
Sample calculation
Instant fit estimate
Underbust29 in
Bust33 in
Your starting size
34D
Includes conversions and sister sizes.
UK 34DEU 75DAU 12D
US / UK / EU / FR / AU
Free, no account
Covers 36 common sizes
Instant results
Measurement types and size chart reference
Start with the calculator, then compare your size.
Converter
Size Converter
Type a US, UK, EU, French or AU size and see the matching labels in the other sizing systems.
Convert a sizePreview result
UK 34D
Bra Size Calculator
Enter your measurements and get a size, conversions, and sister-size options.
Find my sizeSize Converter
Enter a size in one system to compare it across UK, EU, FR, and AU.
Convert a sizeSister Size Finder
Find nearby band-and-cup combinations that may fit more comfortably.
Find sister sizesHow it works
Start with my measurementsA clearer path from measurement to fit.
wearavo keeps the sizing process simple: measure, calculate, compare, then check the real fit before you trust the label.
How to use these tools
Measure first
Use a soft tape and write down your underbust and bust measurements before opening the calculator.
Compare the label
If a retailer uses UK, EU, French, or Australian sizing, convert your result before choosing a size.
Check real fit
Use sister sizes and fit checks when the number looks right but the band, cup, straps, or wire feel off.
Why bra sizing is confusing
Bra sizes combine a band number with a cup step, but different sizing systems do not always use the same labels. A size can look familiar in one country and change letters in another. Brand charts, fabric, and shape also affect the final fit, so a conversion is a starting point, not a guarantee.
Fit checks
Common fit problems
Band rides upA band that climbs at the back usually means the band is not giving steady support.Straps dig inStraps often dig when they are doing too much work or the band is not firm enough.Cup gapCup gaps can come from cup volume, shape mismatch, or a band that changes how the cups sit.Underwire hurtsWire discomfort can come from cup size, wire width, band tension, or style shape.
Popular searches
Popular sizes
Next steps
One result can open several useful next steps.
After you calculate or choose a size, you can check conversions, sister sizes, fit notes, and nearby sizes without starting over.
Ready when you are
Use your measurements to get a starting size, then compare conversions, sister sizes, and fit notes.
FAQ
How accurate is an online bra size calculator?
It is a useful starting point, not a guarantee. Your best size can change by brand, bra style, fabric, and how the cups sit on your body.
How should I measure before using the calculator?
Measure your underbust for the band, then measure around the fullest part of your bust. Keep the tape level and snug, but not tight.
Why is my UK bra size different from my US size?
Sizing systems use different cup labels, especially after D. That is why a direct-looking conversion may still need a brand chart check.
What is a sister size and when should I use one?
A sister size keeps a similar cup volume while changing the band. Try one when the cups are close but the band feels too firm or too loose.
Should I get professionally fitted?
A professional fitting can help if you have pain, post-surgery needs, pregnancy or nursing changes, or a shape that never feels comfortable in standard sizes.
Ready when you are
Ready to check your starting size? Use your underbust and bust measurements to get a quick result.