International Bra Size Converter

International lingerie shopping is one big size puzzle. Enter your underbust and bust in cm and the tool maps them to the correct band & cup, then lays out the equivalent labels in EU, UK, US, AU and JP at a glance. Already know your local size? Switch tabs and reverse-look the other four systems.

Underbust

Snug measure just under the bust (cm) — sets the band. Bust

Measure around the fullest part of the bust (cm). Bust − underbust sets the cup.

Equivalent sizes

Exact match

EU / International: —
UK: —
US: —
AU / NZ: —
JP / HK: —

How to measure

Measure wearing a non-padded bra or unclothed. Keep the tape snug but not tight; bust minus underbust drives the cup (each +2.5 cm = one cup up). In JP / HK, the band number is just the underbust in cm (e.g. 75).

Cross-system chart aggregated from Wacoal, Triumph and ASOS guides; individual brands can sit ±1 cup or band off — always cross-check with the brand's own size chart.

Formula

Band: round underbust to the nearest 5 cm (65 / 70 / 75 / 80 / 85…). EU = JP = HK = underbust_cm; UK = US = EU − 40; AU = (EU − 60) ÷ 2 + 6. Cup: cup_index = round((bust − underbust) ÷ 2.5) A=10 cm, B=12.5, C=15, D=17.5, E/DD=20, F=22.5, G=25 ...

· Chart covers underbust 58–107 cm (EU 60–105 / UK 28–46 / US 28–46 / AU 6–24) with cups A through I (10–30 cm bust-underbust differential).
· EU = JP = HK band number is the underbust in cm; UK, US and AU follow separate numbering (UK and US agree; AU uses a smaller multiplier).
· Cup naming above D diverges between systems: UK DD = EU / JP E, UK E = EU F; some US brands still use DDD = F.
· Sister sizes: drop one band size and add one cup (or vice versa) for roughly the same volume — handy when the band fits but the cup runs off.
· How to measure: in the evening, tape snug but not compressing, keeping the chest in a natural forward-tilted position to avoid flattening the bust.
· Source: aggregated from Wacoal HK, Triumph International and ASOS bra-fit guides (2024). Individual brands can sit ±1 cup or ±1 band off — always cross-check the brand's own chart.

Frequently asked

Why am I a 75C at Triumph but a 34B at Calvin Klein?

Both labels describe roughly the same band and cup: Triumph follows the EU / JP convention where the band number equals underbust in cm (75 cm), while Calvin Klein and other US brands use the inch system (band 34 ≈ 75 cm). The C vs B cup gap is usually brand-naming and pattern drift — every label defines its own "C" volume slightly differently. The reliable approach is to measure your underbust and bust in cm, then cross-check both brands' size charts against those numbers.

My measurements bump me up a cup size — am I measuring wrong?

Most likely you've been on an older "underbust + 5 inches" American formula, which underestimates the band and pushes the cup up — so plenty of people think they're a 34A when they're actually a 32C / 34B. The cm-based approach used here (and on most modern brand charts) is more accurate. If your result lands in the D / DD / E range, remember sister sizes as a fitting fallback: one band down + one cup up gives a similar volume.

Are JP 75C, UK 34C and EU 75C really the same bra?

On paper yes — all three describe a 75 cm underbust and a 15 cm bust-underbust gap (cup C). In practice fit also depends on underwire width, cup cut (half / full / T-shirt), strap elasticity and fabric stretch, so the same label across brands still feels different on the body. When shopping online, pick a retailer with free returns or exchanges so you can size up/down if the first pick doesn't fit right.

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