Bra Size Calculator (US, UK & EU)
Enter bust and underbust to get band, cup, and sister sizes—built for USA and UK shoppers, with EU labels included.
Need steps first? How to measure for bra size
Bra Size Chart (US / UK / EU)
Full bra size chart →Quick reference for common band and cup sizes. Use the calculator below for your exact fit.
| US | UK | EU |
|---|---|---|
| 32A | 32A | 70A |
| 34B | 34B | 75B |
| 36C | 36C | 80C |
| 38D | 38D | 85D |
Enter your measurements to calculate bra size
Measuring Steps:
- Wear your best-fitting bra or no bra
- Measure under bust: snug, level around ribcage
- Measure bust standing: loosely around fullest part while standing straight
- Measure bust leaning: around fullest part while leaning forward 90°
- Keep tape measure parallel to ground
- Record measurements to nearest half unit
Measure at the end of exhale for most accurate results
Bra Sister Size Chart
Sister sizes keep roughly the same cup volume while changing the band. Go down a band and up a cup (or up a band and down a cup). Brands still vary—use this as a starting point.
| Your size (US) | Common sister sizes |
|---|---|
| 32A | 30B · 34AA |
| 32B | 30C · 34A |
| 34B | 32C · 36A |
| 34C | 32D · 36B |
| 34DD | 32E · 36D |
| 36C | 34D · 38B |
| 38D | 36DD · 40C |
Example: 34C ≈ 32D ≈ 36B. If the band rides up, try a tighter sister; if cups gap, try a smaller cup sister on a nearby band.
About Our Bra Size Calculator
Our bra size calculator uses your bust and under-bust measurements to determine your perfect bra size across multiple international standards. Whether you're shopping for US, UK, European, French, or Japanese brands, our calculator provides accurate conversions.
The calculator takes into account the differences between regional sizing standards and provides confidence ratings to help you make informed purchasing decisions.
Our Commitment to Accuracy
We understand that finding the right fit can be challenging due to varying standards. Our calculator's logic is based on the European standard EN 13402, which uses the difference between your bust and under-bust measurements to determine cup size. This method provides a consistent and accurate starting point for your search.
For a comprehensive understanding of global sizing, we refer to the International Organization for Standardization (ISO). The key standards, such as the ISO 8559 series (which defines body measurement and size designation), are developed and managed by the official ISO/TC 133 committee on clothing sizing systems.
Professional Measuring Tips
Best Time to Measure
- • Measure in the afternoon when your body is at its largest
- • Avoid measuring during menstruation when breasts may be swollen
- • Take measurements while standing straight
- • Measure at the end of exhale for consistency
Measuring Technique
- • Use a soft measuring tape, not a rigid ruler
- • Keep the tape parallel to the ground
- • Tape should be snug but not tight for under-bust
- • Tape should be loose for bust measurement
International Bra Size Chart (Example)
| US | UK | EU | Band (cm) | Bust (cm) |
|---|---|---|---|---|
| 32A | 32A | 70A | 68 | 81 |
| 34B | 34B | 75B | 73 | 89 |
| 36C | 36C | 80C | 78 | 97 |
| 38D | 38D | 85D | 83 | 105 |
Please Note: This chart is based on data from our `size-charts.json` file and serves as a general reference. Sizes can vary significantly between different brands and styles. We always recommend checking the specific size guide of the brand you are interested in.
Frequently Asked Questions
How do I use a bra size calculator?
Measure underbust and bust (standing and leaning if possible), enter the numbers, and read band and cup in US, UK, and EU. Then check sister sizes if the band or cup needs a small adjustment.
Is this a USA and UK bra size calculator?
Yes. Results include US and UK labels (and EU and other standards). UK cup letters can differ from US on some larger cups—compare the letter shown for each region.
What is bra cup size?
Cup size is the letter based on the difference between bust and underbust. A larger difference means a larger cup letter on the same band.
What does 34B mean?
34B is a common US size: band near 34 with a B cup. Sister sizes often include 32C and 36A. Confirm with your measurements.
What is DD bra size?
DD is a cup letter one step up from D on many US charts (UK labeling can differ at larger cups). Volume still depends on the band—34DD is not the same as 38DD.
What are sister sizes?
Sister sizes are different bra sizes that hold the same cup volume. For example, 34C, 32D, and 36B are sister sizes. If one size doesn't fit perfectly, try the sister sizes.
How often should I measure my bra size?
You should measure your bra size every 6-12 months, or whenever you experience significant weight changes, pregnancy, or hormonal changes that might affect your body.
Do bra sizes vary between brands?
Yes, bra sizes can vary significantly between brands and styles. Our calculator provides a starting point, but it's always best to try on bras when possible or check brand-specific size charts.
Related Tools & Guides
Bra Size Chart
Cup and band tables with sister size chart.
How to Measure Bra Size
Band, standing bust, and leaning bust steps.
34B Bra Size
What 34B means and which sister sizes to try.
Bra Sister Sizes
Keep cup volume while changing the band.
DD vs DDD Cups
Double D, triple D, and E/F letter differences.
Sports Bra Guide
Support levels once you know your size.
Strapless Bra Guide
Fit tips when the band carries more support.
Plus Size Clothing Chart
Extended apparel sizes to pair with bra fit.
Scoop & Swoop Technique
Settle tissue into the cups after sizing.