How to Measure Your Bra Size at Home: Band, Bust, and Cup

5 min read•June 9, 2026•Reviewed: June 9, 2026

✓Reviewed by Apex Conversion Editorial Team · Last reviewed June 9, 2026

Fitting surveys consistently find that a majority of women wear the wrong bra size — most often a band that is too loose and a cup that is too small. Accurate measurement takes two numbers and five minutes: a snug underbust measurement for the band, and a relaxed bust measurement for the cup. Everything else is arithmetic.

You need a soft measuring tape, a mirror, and an unpadded or lightly lined bra (or no bra). Measure in centimeters if you plan to buy European, Japanese, or Australian brands, or in inches for US and UK brands — or take both and use a converter.

Step 1: Measure Your Band (Underbust)

Wrap the tape directly under your bust, where the band of a bra sits. Keep the tape parallel to the floor all the way around — a tape that rides up in the back is the most common error. Pull it snug, exhale normally, and read the number. This is your underbust measurement.

For US/UK sizing: if the measurement is an even number of inches, that is typically your band size; round odd numbers to the nearest even number, trying the smaller band first since bands stretch with wear. For EU sizing: round to the nearest multiple of 5 cm — a 73 cm underbust wears a 75 band (or a firm 70).

Step 2: Measure Your Bust and Calculate the Cup

Measure around the fullest part of your bust, keeping the tape level and resting on the body without compressing tissue. Stand upright with arms relaxed. The difference between this bust measurement and your underbust measurement determines the cup.

In inches, each inch of difference is one cup letter: 1" = A, 2" = B, 3" = C, 4" = D, 5" = DD (US). In centimeters (EU), the cup brackets are roughly: 12–14 cm = A, 14–16 cm = B, 16–18 cm = C, 18–20 cm = D, 20–22 cm = E. Example: 88 cm bust − 73 cm underbust = 15 cm difference → EU 75B.

Fit Checks and Common Mistakes

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The band provides about 80% of support and should be level across your back on the loosest hook when new — tighten hooks as the band stretches.
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If the center panel between the cups doesn't lie flat against your sternum, the cup is too small; if the cup wrinkles or gaps, it is too large.
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Don't measure over a padded or push-up bra — it adds 2–5 cm to the bust measurement and inflates the cup calculation by one to two sizes.
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Straps digging in usually signal a band that is too loose (the straps are doing the band's job), not straps that are too short.
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Re-measure every year or after weight changes of more than about 5 kg / 10 lb — band size shifts faster than most people expect.

Frequently Asked Questions

Should I add inches to my underbust measurement?

Most modern fitting methods use the snug underbust measurement directly as the band size. The older '+4 inches' method dates from an era of non-stretch fabrics and generally produces bands that are too loose for today's materials.

What if my measurement falls between band sizes?

Try the smaller band first — bands stretch over their lifespan, and a firm band on the loosest hook leaves room to tighten later. If the smaller band feels restrictive, take the larger band with one cup letter smaller (the sister size).

How do I convert my measured size to European or Japanese sizing?

Measure in centimeters: your underbust rounded to the nearest 5 cm is the EU/JP band. The bust-minus-underbust difference maps to EU cups in 2 cm steps starting around 12 cm for A. Use the bra size converter to cross-check against US/UK sizing.

Why do I get different sizes in different stores?

Brands cut to different fit models and band tensions, and some still size with added inches. Treat your measured size as the baseline, expect one size of variation between brands, and prioritize the fit checks (level band, flat center panel, no cup gap) over the label.

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