Bra Size Calculator
Enter your underbust and bust measurements below and get an estimated bra size in seconds. Choose Simple mode for a quick two-measurement estimate, or Advanced mode with six measurements for a more refined result. Both modes support inches and centimeters, plus 7 country sizing systems (US, UK, EU, FR, AUS, JP and IN). If you are unsure about measuring, read how to measure your bra size first.
Enter Your Measurements
Advanced mode uses three underbust and three bust measurements for a more refined estimate. Measuring guide.
How the Calculation Works
The math behind the calculator is straightforward, and understanding it helps you get better measurements:
- Unit conversion. If you enter centimeters, the calculator first converts every measurement to inches by dividing by 2.54. All sizing math runs in inches.
- Band size (Simple mode). The band rule depends on the country you pick: US, UK and IN round your underbust to the nearest even inch (32, 34, 36…); EU and JP round your underbust in centimeters to the nearest 5 (75, 80, 85…); FR adds 15 to the EU band (90, 95, 100…); AUS subtracts 22 from the inch band (10, 12, 14…).
- Cup size (Simple mode). The cup is set from the difference between your bust and your band, rounded to a whole number. A bigger difference means a bigger cup.
- Advanced mode. The band comes from your snug underbust (rounded to the nearest even inch), and the cup comes from the average of your three bust measurements (standing, leaning, and lying) minus the band. Averaging smooths out small measuring errors.
- Cup letters by country. Cup letters diverge between systems — for example, a 4-inch bust-to-band difference is a D cup in US and UK sizing but an E cup in EU, FR and AUS sizing. India follows UK-style cup letters. Pick the country used by the brands you shop.
- An estimate, not a verdict. Sizing varies between brands, styles, and manufacturers, so no formula can guarantee a perfect fit. Use your result as a starting point, try bras on, and adjust from there.
Keep Exploring
Your estimated size is only the beginning. These resources help you measure accurately, convert between systems, and find alternatives when your size is out of stock:
- How to measure your bra size — a step-by-step guide to measuring your underbust and bust at home.
- Bra size chart — US, UK, and EU band and cup sizes in one conversion table.
- Sister size calculator — find alternative sizes with a similar cup volume but a different band.
- US bra size calculator and Bra size calculator UK — country-specific calculators with local charts.
- How to measure your bra size correctly at home, bra size chart: US, UK and EU sizes explained, and how to find the right bra size and understand sister sizes — longer fitting guides on the blog.
Frequently Asked Questions
What do I need before I start calculating?
A soft measuring tape and a few minutes is all it takes. Simple mode needs just your underbust and bust measurements; Advanced mode asks for three underbust measurements (loose, snug, tight) and three bust measurements (standing, leaning, lying). You can measure in inches or centimeters — the calculator converts automatically.
How do Simple and Advanced modes differ?
Simple mode uses one underbust and one bust measurement to produce a quick estimate. Advanced mode takes the average of three bust measurements and uses the snug underbust for the band, which smooths out small measuring errors and usually gives a more refined estimate.
Why does the calculator round my band to an even number?
Bra bands are sold in even-numbered sizes — 32, 34, 36, and so on. To match the sizes you can actually buy, the calculator rounds your underbust measurement to the nearest even inch before calculating your size.
Which country should I pick in the calculator?
Pick the country used by the brands you shop most often. The Country dropdown offers US, UK, EU, FR, AUS, JP and IN sizing — band numbers and cup letters differ between them, so choose the one printed on your size labels. The dedicated country calculator pages include full charts for each system.
Can I enter my measurements in centimeters?
Yes. Choose Centimeters in the unit dropdown and enter your measurements as-is — the calculator converts them to inches by dividing by 2.54 before running the sizing math.
My result is different from the size I usually wear. What should I do?
Treat the result as a starting point, not a verdict. Try it on alongside your usual size and a sister size or two, then pick what feels most comfortable. Band and cup fit both matter, and sizing varies between brands — our disclaimer page explains the limitations in more detail.