Bra Size Calculator — How to Find Your Perfect Fit
This bra size calculator helps you find and convert your bra size to the most common international systems — USA, UK, continental Europe (EU), and Australia. Whether you're shopping domestically or buying from an international retailer, we've got you covered.
Taking Measurements for Correct Bra Size
You need two measurements. Take them while braless or wearing a non-padded bra for maximum accuracy.
- Bust measurement: Measure at the fullest point of your bust with a soft measuring tape. Keep the tape level and not too tight — breathe in and out normally. Round the number up if needed.
- Frame measurement (underbust): Measure around the bottom of the band, directly under your bust. Keep the tape level and snug but not tight. Round up to the nearest whole number.
How to Calculate Bra Size
- Take your measurements as described above.
- Round your underbust up to the nearest even number — this gives your band size.
- Subtract the band size from the bust measurement — this gives the cup difference.
- Match the cup difference to the cup size chart below.
Cup Size Chart
| Difference (in / cm) | US Cup | UK Cup | EU Cup | AU Cup |
|---|---|---|---|---|
| <1 / <2.5 | AA | AA | AA | AA |
| 1 / 2.5 | A | A | A | A |
| 2 / 5.1 | B | B | B | B |
| 3 / 7.6 | C | C | C | C |
| 4 / 10.2 | D | D | D | D |
| 5 / 12.7 | DD | DD | E | DD |
| 6 / 15.2 | DDD | E | F | E |
| 7 / 17.8 | DDDD | F | G | F |
| 8 / 20.3 | H | FF | H | G |
| 9 / 22.9 | I | G | I | H |
| 10 / 25.4 | J | GG | J | I |
Sister Sizes
A sister size is a bra with a different band and cup letter combination, but the same physical cup volume. If your usual size is unavailable, a sister size can provide an equivalent fit.
The rule is simple:
- Go one band size down + one cup size up = same cup volume
- Go one band size up + one cup size down = same cup volume
Example: 34C is a sister size of 32D and 36B. All three have the same cup volume.
US vs. UK vs. EU Sizing
| US Band | UK Band | EU Band |
|---|---|---|
| 28 | 28 | 60 |
| 30 | 30 | 65 |
| 32 | 32 | 70 |
| 34 | 34 | 75 |
| 36 | 36 | 80 |
| 38 | 38 | 85 |
| 40 | 40 | 90 |
| 42 | 42 | 95 |
| 44 | 44 | 100 |
Making Sure Your Bra Fits
- The band should be firm but not uncomfortable — you should be able to slide two fingers under it.
- The underwire should lie flat against your chest, not float over breast tissue.
- There should be no spillage at the top or sides of the cups.
- The center gore (the part between the cups) should lie flat against your sternum.
- Straps should stay in place without digging into your shoulders.
Signs Your Bra Doesn't Fit
- Band rides up in the back → band too large, go down a size
- Straps digging in → cups too small or band too large
- Cups gaping → cups too large
- Spillage → cups too small, go up a size
- Four-breast effect → cups too small
- Underwire poking → cup size too small or wrong shape
Bras for Special Tasks
- Sports bra: High-impact support, encapsulation or compression style recommended for sizes D+
- Nursing bra: Look for extra-wide straps and easy-open clasps
- Strapless bra: Band should be one size firmer than usual; silicone grip helps
- Minimizer bra: Redistributes volume for a smoother silhouette under fitted clothing
- Full-bust bra (DD+): Look for seamed cups and wide-set straps for the best support
Frequently Asked Questions
How often should I get remeasured?
Weight changes, pregnancy, nursing, and aging can all affect your bra size. It's a good idea to remeasure every 12 months or after any significant body change.
Should I measure in inches or centimeters?
Either works — our calculator supports both imperial (inches) and metric (cm). US and UK bra sizes use inches; EU sizes use centimeters.
What if my measurements fall between sizes?
If your underbust is an odd number of inches, round up to the next even number to get your band size. If your bust measurement is between sizes, try both the larger and smaller cup first.
Do I need a different size for every brand?
Yes — sizing varies between brands and even styles within the same brand. Use your measurements as a starting point, then try multiple sizes when possible.
What is the most common bra size?
Studies suggest 34B is the most common size in the US, though many experts believe a significant percentage of women are wearing the wrong size. Getting professionally fitted is always recommended.