UK Bra Size Calculator
Find your perfect bra size in seconds. Measure your underbust and overbust, enter the numbers below, and get your UK size, cup letter, sister sizes, and an international conversion — all in one place.
Bra Size Calculator
Enter your measurements to find your UK bra size
Measurement directly under your bust
Measurement around the fullest part
Your UK Bra Size
Band size, cup letter, and international equivalents
Enter your underbust and overbust measurements, then click Find My Bra Size to see your result.
Bra Fitting Tips
A size is just a starting point. These signs will tell you if your bra actually fits correctly.
The Band Should Do Most of the Work
Around 80% of support comes from the band, not the straps. On a new bra, fasten on the loosest hook — you can tighten as the fabric stretches over time. You should be able to fit two fingers under the band at the back, no more.
No Spillage or Gaps at the Cup
The cup should enclose all breast tissue with no bulging over the top or sides (too small) and no gaping or wrinkling (too large). If you have spillage, go up a cup; if the cup gapes, go down a cup.
The Centre Gore Should Lie Flat
The bridge between the cups should sit flat against your sternum. If it lifts away from your body, the cups are too small. Try going up a cup size — or use a sister size with a smaller band.
Straps Shouldn’t Bear the Load
Straps should sit comfortably without digging in or slipping off. If you’re constantly adjusting them, the issue is usually a band that’s too loose rather than strap tension. A well-fitting band keeps everything in place.
Use Sister Sizes When You’re Between Sizes
If your calculated size feels slightly off, try a sister size — same cup volume, different band and letter. For example: if 34C is slightly loose in the band, try 32D. The cup volume is identical.
Re-measure Every 12–18 Months
Weight changes, hormonal shifts, pregnancy, and ageing all affect bra size. Many people find they’ve been wearing the wrong size for years. Re-measuring annually ensures ongoing comfort and support.
UK Bra Size Chart
Common UK bra sizes with band measurements, cup differences, and international equivalents. Scroll right on mobile to see all columns.
| UK Size | Band (in) | Bust Diff | Cup | US Size | EU Size | AU Size |
|---|---|---|---|---|---|---|
| 30A | 28–30″ | 1″ | A | 30A | 65A | 8A |
| 30B | 28–30″ | 2″ | B | 30B | 65B | 8B |
| 32A | 30–32″ | 1″ | A | 32A | 70A | 10A |
| 32B | 30–32″ | 2″ | B | 32B | 70B | 10B |
| 32C | 30–32″ | 3″ | C | 32C | 70C | 10C |
| 32D | 30–32″ | 4″ | D | 32D | 70D | 10D |
| 34A | 32–34″ | 1″ | A | 34A | 75A | 12A |
| 34B | 32–34″ | 2″ | B | 34B | 75B | 12B |
| 34C | 32–34″ | 3″ | C | 34C | 75C | 12C |
| 34D | 32–34″ | 4″ | D | 34D | 75D | 12D |
| 34DD | 32–34″ | 5″ | DD | 34DD | 75E | 12DD |
| 34E | 32–34″ | 6″ | E | 34DDD | 75F | 12E |
| 36A | 34–36″ | 1″ | A | 36A | 80A | 14A |
| 36B | 34–36″ | 2″ | B | 36B | 80B | 14B |
| 36C | 34–36″ | 3″ | C | 36C | 80C | 14C |
| 36D | 34–36″ | 4″ | D | 36D | 80D | 14D |
| 36DD | 34–36″ | 5″ | DD | 36DD | 80E | 14DD |
| 38B | 36–38″ | 2″ | B | 38B | 85B | 16B |
| 38C | 36–38″ | 3″ | C | 38C | 85C | 16C |
| 38D | 36–38″ | 4″ | D | 38D | 85D | 16D |
| 40C | 38–40″ | 3″ | C | 40C | 90C | 18C |
| 40D | 38–40″ | 4″ | D | 40D | 90D | 18D |
Bra Size FAQ
Answers to the most common questions about measuring and finding the right UK bra size.
You need a soft measuring tape. First measure your underbust (directly under your bust, pulling the tape snugly) to get your band size — round up to the nearest even number. Then measure your overbust (around the fullest part of your chest, tape resting lightly). Subtract the band from the bust; the difference gives your cup size. Enter both into this calculator for an instant result.
UK cup sizes go: AA, A, B, C, D, DD, E, F, FF, G, GG, H, HH, J, JJ, K. Each step represents roughly one inch of difference between your bust and band measurement. So a 1-inch difference = A cup, 2 inches = B cup, 3 inches = C cup, 4 inches = D cup, 5 inches = DD cup, and so on. UK sizing uses double letters (DD, FF, GG) rather than moving straight to the next letter.
Sister sizes are bra sizes that share the same cup volume but use different band and letter combinations. For example, 32D, 34C, and 36B are all sister sizes — the actual space inside the cup is identical. Knowing your sister sizes is useful when your calculated size isn’t available in a particular style, or when a bra feels right in the cup but slightly off in the band.
Band sizes are the same in UK and US (both use inches). Cup sizes match up to D, but diverge above that. UK DD = US DD, UK E = US DDD (or F), UK F = US DDDD (or G), and so on. The US tends to repeat D letters rather than using the UK’s alphabetical extension system. When buying from US brands, always check a conversion chart for larger cup sizes.
EU band sizes are in centimetres and are typically the UK band size multiplied by 2.54, then rounded — so a UK 34 band = EU 75, UK 36 = EU 80, UK 38 = EU 85. EU cup letters broadly match UK up to C, but EU uses single letters beyond D (EU E = UK DD, EU F = UK E), whereas UK uses double letters. Always check a conversion chart when buying from European brands.
Bra sizing is not standardised across brands. Different manufacturers use different cup shapes, fabric elasticity, and grading methods. A 34C from one brand may fit completely differently to a 34C from another. This is normal. Use your measurements as a guide and always try before you buy when possible, or check the brand’s specific size guide and returns policy when shopping online.
UK bra sizes are traditionally calculated in inches — this is how the standard band sizes (28, 30, 32, 34, 36 etc.) are derived. However, this calculator accepts both inches and centimetres and converts automatically. If you have a metric tape measure, simply select centimetres and enter your measurements — the calculator handles the rest.
It is worth re-measuring every 12 to 18 months, or after significant life changes such as weight fluctuation (gain or loss of roughly half a stone or more), pregnancy, breastfeeding, or hormonal changes. Many women discover they have been wearing the wrong size for years after a professional fitting or re-measurement. Getting the right size makes a significant difference to both comfort and posture.