The best free online bra size calculator UK — accurate, easy and completely free. Wondering what bra size am I? Our easy UK bra size calculator gives instant NHS-standard results in inches or cm, with visual guides, sister sizes, and international conversions.
The most accurate and best online bra size calculator UK women trust. Want to know how to calculate your bra size UK? Simply enter two measurements — underbust and bust — in inches or cm. This free online bra size calculator UK nhs-standard tool works out your band size, cup size, sister sizes, and international conversions in seconds.
Measure snugly around your ribcage, directly under your breasts.
Measure comfortably around the fullest part of your bust.
Measuring your bra size at home is straightforward with the right technique. Follow these three NHS-recommended steps for working out your bra size UK — you’ll need a soft measuring tape and can measure in either inches or cm. Our free online bra size calculator UK will do the rest — this is exactly how to measure bra size UK: underbust for band, bust for cup.
Wrap the tape directly under your breasts, around your ribcage. Keep it horizontal and breathe normally.
Measure around the fullest part of your bust. The tape should sit comfortably — not pulled tight.
Enter both figures into our bra size calculator UK above for your UK size, sister sizes, and 4 international formats including US and EU.
Our bra size calculator UK charts cover every band and cup combination in both inches and centimetres, following the same NHS-standard method. Use these tables to understand how to calculate cup size UK — and as a quick reference alongside the online calculator above.
| UK Band | Underbust (cm) | Underbust (inches) | Frame Type |
|---|---|---|---|
| 28 | 63–67 | 25–26½" | Extra Petite |
| 30 | 68–72 | 27–28½" | Petite |
| 32 | 73–77 | 29–30½" | Small |
| 34 | 78–82 | 31–32½" | Average |
| 36 | 83–87 | 33–34½" | Average |
| 38 | 88–92 | 35–36½" | Full |
| 40 | 93–97 | 37–38½" | Full |
| 42 | 98–102 | 39–40½" | Extended |
| 44 | 103–107 | 41–42½" | Extended |
| 46 | 108–112 | 43–44½" | Plus |
| UK Cup | Difference (in) | Difference (cm) | Volume |
|---|---|---|---|
| AA | <1" | <2.5 | Very Small |
| A | 1" | 2.5 | Small |
| B | 2" | 5 | Modest |
| C | 3" | 7.5 | Medium |
| D | 4" | 10 | Full |
| DD / E | 5" | 12.5 | Full Plus |
| E / F | 6" | 15 | Large |
| F / FF | 7" | 17.5 | Large Plus |
| FF / G | 8" | 20 | Very Large |
| G / GG | 9–10" | 22.5–25 | Extended |
| H | 11" | 27.5 | Extended Plus |
| HH / J | 12" | 30 | Super Extended |
| UK | US | EU | France / Belgium | Australia |
|---|---|---|---|---|
| 30A | 30A | 65A | 80A | 10A |
| 32B | 32B | 70B | 85B | 12B |
| 34C | 34C | 75C | 90C | 14C |
| 34D | 34D | 75D | 90D | 14D |
| 34DD | 34E/DDD | 75E | 90E | 14DD |
| 36E | 36DDD | 80F | 95F | 16E |
| 38F | 38G | 85G | 100G | 18F |
| 40FF | 40H | 90H | 105H | 20FF |
| 42G | 42I | 95I | 110I | 22G |
Once you’ve used our bra size calculator to find your size, here’s how to tell if the fit is truly right. These are the signs UK fitting experts check for.
Our calculator uses the modern UK sizing method — underbust measurement directly for band size, and the difference between bust and band for cup. This is the standard used by Bravissimo, M&S and most UK lingerie specialists. Results may vary slightly between brands, so we always recommend trying on before purchasing.
Band sizes are numerically the same. The cup naming diverges from D onwards — UK "DD" equals US "E", and UK "E" equals US "DDD/F". Always check our conversion chart when ordering from US brands.
Sister sizes have the same cup volume with adjacent band and cup combinations. For example, 34D, 36C, and 32E all hold the same amount of breast tissue. If a brand doesn't carry your exact size, try a sister size — the fit will be very similar.
Measure without a bra, or wearing an unpadded bralette. Padded bras add extra volume which skews the cup measurement. Stand upright, breathe normally, and keep the tape parallel to the floor throughout.
Re-measure every 6–12 months, or after any significant weight change, pregnancy, breastfeeding, or hormonal change. Bra size can shift more than most people realise — even a few kilograms can change both the band and cup.
Every brand cuts bras differently — cups may run small or large, and band stretch varies. Use your calculated size as a starting point and adjust by ±1 cup or band as needed. This is completely normal and expected when shopping across different labels.
To calculate your bra size UK, measure your underbust in inches or cm for your band size, then measure around the fullest part of your bust. The difference between the two gives your cup size. Enter both into our bra size calculator UK above and get your full result instantly — band, cup, sister sizes, and international conversions. The same method works whether you prefer inches or centimetres.
Working out your bra size UK at home is easy without a professional fitter. Use a soft measuring tape for your underbust (directly under your breasts) and your bust (around the fullest point). Enter both into our free bra size calculator UK — it follows the same NHS-recommended method used by UK lingerie specialists, so you get an accurate result without leaving home.
Our bra size calculator UK automatically shows your US and EU equivalents in the results. UK and US band sizes are numerically the same, but cup letters diverge from D onwards. For EU sizes, the band adds roughly 15 to the UK number (e.g. UK 34 = EU 75). Use the International tab in our size chart above for a full UK to US and UK to EU reference table.