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". See our full UK vs US vs EU conversion guide when ordering from US brands.
Sister sizes have the same cup volume with adjacent band and cup combinations. For example, 32D, 34C, and 36B 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 calculator above for your full result — band, cup, sister sizes, and international conversions. See our full how to measure guide for a step-by-step walkthrough.
Working out your bra size at home is easy without a professional fitter. Use a soft measuring tape for your underbust and your bust, then enter both into our free calculator — it follows the same method used by UK lingerie specialists. Read our full guide on how to work out your bra size for every way people ask this question answered in one place.
Our calculator 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 41 to the UK number (e.g. UK 34 = EU 75). See our UK vs US vs EU bra sizes guide for the full reference table.
UK sizes run from around 28AA up to 44G and beyond, with sister sizes filling the gaps in between. Mainstream shops usually stock up to a 44G or 46GG; specialist and made-to-measure fitters go further in both directions. See our full UK bra sizes guide for the complete size list and chart.
Yes — pregnancy, breastfeeding, and high-impact activity all need a slightly different approach to sizing than an everyday bra. See our specialty bra size calculators guide for maternity, nursing, sports, strapless, plus-size and first-bra sizing advice.
Most UK department stores and lingerie specialists offer free, no-obligation bra fittings. Our online result is accurate as a starting point, using the same method a professional fitter uses. See our full bra fitting guide for what to expect and how to tell if a bra actually fits once you try it on.