Bra Size Converter – True Value Calc

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Bra Size Calculator

Lingerie • US/UK/EU/FR/AU

Measurement units

Underbust / band measurement ⓘ

Bust measurement (fullest part) ⓘ

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Enter your measurements to calculate your size

How to Use the Bra Size Calculator

Choose your units — inches or centimeters.
Measure your band — wrap the tape snugly around your ribcage, directly under your bust, and enter the number.
Measure your bust — measure loosely around the fullest part and enter it.
Read your size — your bra size is calculated instantly in US, UK, EU, French and Australian sizing, with your primary size highlighted.

Why Use This Bra Size Calculator

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Accurate Standards

Built on internationally recognised SI and standards-body conversion factors for dependable results.

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Instant & Animated

Results update live as you type, with a clear visual breakdown across every unit at once.

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100% Private

Everything runs in your browser — no account, no uploads, nothing leaves your device.

Understanding the Bra Size Calculator

A bra size combines two measurements: the band (the firm circumference around your ribcage, directly under the bust) and the cup (the difference between your bust and your band). The lettered-cup system was introduced by S.H. Camp and Company in 1932 and popularised by Warner's, and is now expressed differently around the world.

How this calculator works. Your underbust measurement is rounded to the nearest even inch to give the band (e.g. 31″ → 32). The cup is then taken from how many inches your bust is larger than your band: each inch is one cup up — about 1″ = A, 2″ = B, 3″ = C, 4″ = D, 5″ = DD, 6″ = DDD/F, and so on. The result is then expressed in US/Canada, UK, EU (EN 13402), France/Spain and Australia/New Zealand standards. For example, a 32″ band with a 36″ bust is a US 32D, UK 32D, EU 70D and French 85D.

Because every brand and style fits a little differently, treat the result as an accurate starting point rather than a guarantee — if a band feels tight or loose, try the "sister size" (go down a band and up a cup, or up a band and down a cup) for the same cup volume.

Bra Size Calculator FAQ

How do I measure for my bra size? ▾

Take two measurements with a soft tape. For the band, wrap the tape snugly around your ribcage directly under your bust, level all the way around. For the bust, measure loosely around the fullest part. Enter both into the calculator (inches or centimetres).

How is cup size calculated? ▾

Cup size comes from the difference between your bust and band measurements. Roughly each inch of difference is one cup: 1″ = A, 2″ = B, 3″ = C, 4″ = D, 5″ = DD, 6″ = DDD. A 3″ difference on a 34″ band is a 34C.

What is a sister size? ▾

A sister size has the same cup volume on a different band. Going down a band size and up a cup (e.g. 34C → 32D), or up a band and down a cup (34C → 36B), keeps a similar fit — useful when your exact band feels too tight or loose.

How do EU and French bra sizes compare to US? ▾

EU bands are the underbust in centimetres (a US 34 ≈ EU 75), and France/Spain add 15 to the EU band (EU 75 = FR 90). So a US 34C is an EU 75C and a French 90C. This calculator shows all of these at once.

How accurate is this bra size calculator? ▾

It uses the standard band-and-cup method also used by major fitting guides, so it gives a reliable starting size. Real fit still varies by brand, style and body shape, so use it as a guide and try sister sizes if needed.