Cuppa

Find your bra size

Enter your measurements taken with a soft tape measure. The result updates as you type and is converted to the sizing standards of the main countries.

Your measurements

The starting values are an example: replace them with your own.

Measure without a bra, or in an unpadded one.
Keep the tape parallel to the floor.
Take all underbust measurements at the same point of your breathing.
Dashed line: bust. Yellow line: underbust.

Underbust (ribcage)

Snug

Tape as snug as you want a band to feel: it stays put but does not squeeze. Read it at the end of a normal breath out.

Tight optional

Breathe out, then pull the tape as tight as you can.

Loose optional

Tape resting on the skin without pulling.

Bust (fullest point)

Standing

Upright, arms by your sides, without flattening the breasts.

Leaning forward recommended

Bend at 90°, back parallel to the floor.

Lying down optional

Lying on your back, tape over the fullest point.

Your size

–

Cup on the tape: bust − band difference in inches

All standards

Sister sizes (same cup volume)

For comparison: official EU chart (EN 13402)

How it was calculated

Check the fit in the mirror

The calculation is a starting point: brands and styles fit differently. Check these five points on an underwired bra fastened on the loosest hook.

Band

Stays level all the way round. If it rides up your back, try one band down and one cup up; if it digs in, do the opposite.

Cup

Holds the whole breast. If you spill over the top or sides, go up a cup; if the fabric wrinkles, go down.

Underwire

Follows the crease under the breast and reaches towards the armpit without resting on breast tissue.

Centre front

The piece between the cups lies flat on the breastbone. If it lifts away, the cup is too small.

Straps

Neither slip nor dig in. Support should come from the band, not the straps.

Method and sources

Band from the raw underbust. The band is the snug underbust in inches rounded to the nearest even number, with nothing added. McGhee and Steele (British Journal of Sports Medicine, 2006) recommend raw underbust values for the band and a fixed breathing state while measuring, because breathing in makes the band come out larger and the cup smaller. Study
Why not the traditional chart. White and Scurr (University of Portsmouth, Ergonomics, 2012) compared tape-measure sizing with professional fit criteria in 45 women: the traditional method overestimated the band and underestimated the cup, more so at larger sizes. Study record
Six measurements. The rules come from the manual sizing guide of the A Bra That Fits community, written and refined by its members: use the leaning bust, or the average of the bust measurements when leaning and standing differ by more than 2.5 inches; go down a band when snug and tight differ by 4 inches or more. Between two bands, the lower one is chosen only if the tight measurement fits inside it.
Cup. Each inch (2.54 cm) between bust and band size is one cup, starting from A = 1 inch. Because the cup is counted from the band, the same letter holds a different volume on a different band: McGhee and Steele (2011) measured this in 104 women and advise thinking of a size as band and cup together. Study
Conversions. Band: UK and US in inches; EU in cm in steps of 5 (UK 32 = EU 70); France, Spain and Belgium = EU + 15; Italy 1 = EU 65, 2 = EU 70 and so on; Australia and New Zealand = UK − 22. Cups: UK scale with double letters (DD, FF, GG…), US scale (DD/E, DDD/F, G, H, I…), EU scale with single letters. Reference charts: Bra sizing by country, Brastop.
EN 13402 comparison. The European standard labels the band as the underbust rounded to 5 cm and the cup from bust minus underbust in 2 cm steps (A = 12 to 14 cm). It is shown separately because it leads to a different label from the converted size. Table
Limits. No formula has been validated as exact: the studies agree on the direction (firmer band, larger cup than traditional charts), and expect the result to be within about one band or cup of your best fit. Cups go up to M on the UK scale. Past DD, US letters vary by brand, and some Italian brands use EU letters. The five fit criteria are those of the Portsmouth study.