How to measure bra size?

To measure your bra size you need two measurements, taken in this order. Your under-bust — the tape held firm directly under the bust — gives your band size. Your upper-bust minus your under-bust gives your cup size. Wear an unpadded bra, stand relaxed with your arms down, and keep the tape level all the way round.

How do I measure my bra size at home?

Three steps, about five minutes, with a soft tape measure. Wear an unpadded bra — measuring over a padded or push-up bra adds volume to the upper-bust reading and gives a cup size that is too large.

Step 3 — Subtract. Upper-bust minus under-bust gives your cup size. An upper-bust of 88 cm and an under-bust of 75 cm is a difference of 13 cm, which is a B cup. The under-bust of 75 cm puts the band at 75 / 34. The size is 75B.

How do I calculate my cup size?

Subtract your under-bust measurement from your upper-bust measurement. The difference in centimetres is your cup size.

Difference between upper-bust and under-bust	Cup size
9 - 11cm	A
11.5 - 13.5cm	B
14 - 16cm	C
16.5 - 18.5cm	D
19 - 21cm	E
21.5 - 23.5cm	F

How do I find my band size?

Your band size comes from the under-bust measurement on its own — no subtraction. Wacoal Singapore labels both the Japanese and UK notation, so 75 / 34 is one band, written two ways.

If your under-bust is between	Your band size is
68 - 72cm	70 / 32
73 - 77cm	75 / 34
78 - 82cm	80 / 36
83 - 87cm	85 / 38
88 - 92cm	90 / 40
93 - 97cm	95 / 42
98 - 107cm	100 / 44

The full charts, including bra tops, camisoles and sports bras, are on the Wacoal bra size chart.

How tight should the tape be?

Different for each measurement, and this is where most home measurements go wrong. For the under-bust, pull the tape firm — it should sit snug against the ribcage without digging in. For the upper-bust, keep it loose and level, resting on the fullest point without compressing the breast tissue. Pulling the upper-bust tape tight is the single most common reason a home measurement comes out a cup size too small.

How do I know the size I measured actually fits?

A tape gives you a starting size, not a fit. Check these five things on the bra itself.

1. The band is level. Front and back sit on the same line, parallel to the floor. If it rides up at the back, the band is too big.
2. Two fingers, no more. Two fingers should slide under the band with light resistance, on the loosest hook.
3. The cups are smooth. No gap at the top edge, nothing spilling over the top or out at the side.
4. The centre lies flat. The gore between the cups touches your breastbone. If it floats away, the cups are too small.
5. The straps stay put. They neither slip off the shoulder nor leave a groove after a few hours. Straps carry about 10% of the support — the band does the rest.

Any one of these failing is enough to change the size. There is more detail in why a bra rides up, gaps or digs.

Frequently asked questions

Should I measure with a bra on or off?

With an unpadded, non-push-up bra on. Measuring topless changes where the fullest part of the bust sits and gives an inconsistent upper-bust reading; measuring over padding adds volume that is not yours.

What if my measurement falls between two sizes?

Take the smaller band and try the cup on either side of what the chart gives. Bands stretch with wear, and cup shape differs between styles, so the chart size is a starting point rather than a verdict.

How often should I re-measure?

Every six to twelve months, and after any weight change, pregnancy or breastfeeding. Band size in particular changes more than most people expect.

What is a sister size?

A different band and cup combination holding the same cup volume. If the band is too loose, go down one band and up one cup — 80C becomes 75D. If it is too tight, go up one band and down one cup. See the size guide.

Can I measure myself, or do I need someone to help?

You can do both measurements yourself in front of a mirror. Check in the mirror that the tape is level all the way round at the back — a tape that slopes upward at the back is the second most common source of error.

The next step

With your two measurements, read them off the bra size chart. If you would rather be measured properly, Wacoal Singapore offers a professional bra fitting in store, where a fitter can see how the band sits and which cup shape suits you. Find your nearest Wacoal store.