Estimate a starting bra band and cup from underbust and full-bust measurements using clearly labeled US, UK or EU sizing conventions.
01 / TWO MEASUREMENTS
Use the country and chart used by your garment. These are fitting estimates; manufacturer charts and an actual fit check take priority.
MEASURE WITH CONFIDENCE
Measure directly beneath the bust. Keep the tape level and comfortably snug, without digging in.
Measure around the fullest bust with the tape resting lightly. Stand naturally; an unpadded, well-fitting garment can help.
02 / STARTING FIT ESTIMATE
Enter two measurements to see a starting size, band/cup breakdown and nearby sister sizes.
Already know your bra size? Choose its country and convert the label to another sizing system.
This converts the size printed on a garment label. It does not recalculate a size from your measurements. Some country pairs are unavailable; check the brand’s own chart before buying.
03 / FIT & REGIONAL CHARTS
US/UK retain nearest even-inch no-addition bands and optional whole-inch +4/+5 bands, with distinct US and UK cup sequences. FR/BE/ES uses EU bands +15, with EU cup labels. EU retains measured bust minus underbust, AA at 10–under 12 cm and 2 cm intervals thereafter.
AU/NZ uses the cited Berlei chart, not UK letters: 65 cm band →8, 70→10, 75→12; cups A/B/C/D/DD/E/F/G/H in 2 cm intervals starting at bust minus rounded metric band 12–under 14 cm. Other Australian brands use different charts.
JP and KR are separately sourced: each uses measured underbust rounded to 5 cm and 2.5 cm cup centers (AA 7.5, A 10, B 12.5 cm). Midpoint ties round upward. Supported JP bands 65–100, cups AA–H; KR Vivien bands 70–90, cups AA–G. Japanese labels put the cup first. Shared increments in these charts do not make all Asian systems identical.
CN support is deliberately limited to explicitly paired Aimer labels: 70A/B/C↔32A/B/C; 75A/B/C↔34A/B/C; 80A/B/C↔36A/B/C; 85A/B/C↔38A/B/C. The source does not justify a complete CN measurement formula or larger-cup conversion.
Intervals use the lower bound inclusively and upper bound exclusively. Software bounds remain underbust 55–150 cm and full bust ≤200 cm; regional chart bounds can be narrower. Nothing is extrapolated outside the supported charts. All measurements remain browser-local; no photos, uploads, accounts or personal profiles are needed.
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Measure snug underbust and fullest bust, choose units and sizing system, then calculate a starting size. Review the convention and optional sister sizes; manufacturer fitting charts take priority.
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US/UK default to a modern no-addition estimate: underbust in inches rounded to the nearest even band. An optional traditional method rounds underbust to a whole inch, then adds four to even or five to odd measurements. EU bands use underbust centimeters rounded to the nearest five.
US uses AA, A, B, C, D, DD, DDD, G, H and onward. UK uses AA, A, B, C, D, DD, E, F, FF, G, GG, H, HH, J, JJ. The supported EU sequence is AA through K without doubled letters.
US/UK use full bust minus the suggested inch band: less than one inch is AA, otherwise round to a whole-inch difference. EU uses full bust minus measured underbust: 10–under 12 cm is AA, 12–under 14 is A, and successive 2 cm intervals advance cups. Unsupported differences return an error rather than inventing a cup.
No. The regional suggestions are independently calculated using the selected conventions, not guaranteed equivalent labels. Manufacturer cup progressions, band stretch and sizing methods vary; use the brand's chart and an actual fit check.
Within a selected system, one band step up paired with one cup step down, or one band down with one cup up, is an approximate sister size. Similar labeled capacity does not guarantee the same fit.
Measure snug and level immediately below the bust, without compressing skin, then loosely around the fullest bust while standing naturally. The result is a starting fit estimate, not a universal size or an assessment of your body. No photos or uploads are required.