Bra Atlas

How to measure your bra size, step by step

Two tape measurements: snug under the bust for the band, loose around the fullest point for the bust. Breathe out for the first, lean forward for the second if your tissue is soft, and the cup is just the difference between the two.

Standing: underbust and bust tape positions A line drawing of a dress form wearing a bra. A snug, level tape sits just under the bust along the band line; a looser, level tape sits around the fullest point. bustloose underbustsnug, level
Standing: tape snug under the bust, then loose at the fullest point.
Leaning: the bust measured bent forward A simple side-view line drawing of a person bent forward at the hips with the back level and arms relaxed. A loose tape loops around the fullest point of the bust. bust, loose,at the fullest point
Leaning forward: a truer fullest point if the tissue is soft or wide-set.
  1. Underbust. Stand straight, arms down. Wrap the tape around your ribcage directly under the bust, where a bra band sits. Keep it level at the back, pull it snug, breathe out and read it. Round to the nearest even inch for the band.
  2. Bust. Wrap the tape around the fullest part of the bust, level and resting on the skin without pressing in. If the tissue is soft or wide-set, lean forward at the hips first for a truer fullest point.
  3. The cup. Subtract the underbust from the bust. Each inch of difference is one cup letter: 1 is A, 2 is B, 3 is C, 4 is D, 5 is DD.

By Rai Ansar · Sizes computed by the Bra Atlas engine, sources checked · How this page was made

"how to measure bra" gets about 14,800 Google searches a month in the US (Google Ads data, 26 September 2026).

Four mistakes that throw the result off

Each one moves the reading in a predictable direction.

Breathing in for the underbust

A snug underbust is measured after you breathe out, not while holding your breath in. Breathing in shrinks your ribcage and gives a band that is too small.

Pulling the bust tape tight

The bust tape sits loose, resting on the skin without pressing in. A tight bust tape undercounts the bust and makes the cup letter come out smaller than it is.

Letting the tape ride up at the back

Check a mirror or a photo: both tapes should stay level all the way round. A tape that rides up the back reads short.

Measuring over a padded or moulded bra

Padding and moulding change both numbers. Measure over an unlined bra or none at all.

Why the leaning check matters

A Bra That Fits asks for three bust measurements, standing, leaning forward and lying down, and takes the largest of the three, because tissue that is soft or wide-set does not always settle at its fullest point while you stand upright. Leaning forward at the hips, back level, lets it fall forward into the tape. If your three readings differ, use the largest bust figure with your standing underbust.

Once you have both numbers, the calculator shows the size on both the measured-band method and the older +4 method, in UK, US, EU, French, Australian and Japanese labels, and explains why two calculators can give different answers from the same tape.

Quick answers

What do I need to measure my bra size?

A soft tape measure and a mirror. No app or special equipment is needed.

Should I measure over a bra or without one?

An unlined, unpadded bra or no bra at all. A padded or moulded bra changes both the underbust and the bust reading.

Why do I need to lean forward to measure my bust?

If your tissue is soft or wide-set, standing upright can miss the fullest point. Leaning forward at the hips lets it fall forward into the tape, which is why A Bra That Fits asks for a standing, a leaning and a lying bust measurement and uses the largest.

How often should I measure again?

Weight change, pregnancy, surgery and simply time can all move your size. Measure again if a bra that used to fit starts riding up, digging in, gaping or spilling.

Other tools

Sources

Each source was opened and checked on the date shown, or on 25 September 2026. Where sources disagree, the page says so instead of picking one silently.

  1. A Bra That Fits calculator (community calculator of r/ABraThatFits): we submitted 18 measurement pairs in 6 systems on 25 September 2026; raw output is in our repository
  2. Victoria's Secret UK, "Measure Your Bra Size": band = snug underbust rounded to the nearest even number; fit fixes; sister table (opened 26 September 2026)
  3. Wikipedia, "Bra size": UK and US cup ladders, the +4 method, EN 13402 and JIS cup steps
  4. McGhee DE, Steele JR. Optimising breast support in female patients through correct bra fit. J Sci Med Sport 2010;13(6):568-572: 104 women in Australia; 85% in ill-fitting bras