bust size calculator uk

How this bust size calculator UK tool works

This calculator gives you a practical starting point for UK bra sizing. It uses two measurements:

• Underbust: around your ribcage, directly under the bust.
• Full bust: around the fullest part of your bust, keeping the tape level.

From these numbers, it estimates a band size and cup size in the UK system (for example: 32DD, 34F, 36G).

Understanding UK bra sizing

Band size (the number)

The band size is based mainly on your underbust measurement and is shown as an even number in inches, such as 28, 30, 32, 34, and so on.

Cup size (the letters)

In UK sizing, cup letters increase in this order:

AA, A, B, C, D, DD, E, F, FF, G, GG, H, HH, J, JJ, K...

Notice that UK sizes use double letters like DD, FF, and GG, which is one reason UK and US labels may not always match.

How to measure correctly at home

1) Measure underbust snugly

Wrap the tape around your ribcage, just under your bust. Keep it straight around your back and snug (not painfully tight). Breathe out gently before reading the number.

2) Measure full bust comfortably

Measure around the fullest part of your bust, usually over the nipples. Keep the tape level and not compressing breast tissue.

3) Use a mirror if possible

A mirror helps ensure the tape is horizontal all the way around. A twisted or slanted tape can throw off size estimates.

Cup difference guide (UK)

Your cup estimate comes from the difference between full bust and band size (in inches). A simplified chart:

• 1 inch difference = A cup
• 2 inches = B cup
• 3 inches = C cup
• 4 inches = D cup
• 5 inches = DD cup
• 6 inches = E cup
• 7 inches = F cup
• 8 inches = FF cup
• 9 inches = G cup

Brands may vary slightly, so your perfect fit can shift by one cup or one band depending on design and fabric stretch.

Example calculation

Suppose your measurements are:

• Underbust: 79 cm
• Full bust: 95 cm

Converted to inches, that is about 31.1 in underbust and 37.4 in bust. The nearest even band is usually 32. The bust-band difference is about 5.4 in, which typically lands around a DD (or sometimes E depending on brand). Estimated starting size: 32DD.

Why your “calculator size” is a starting point

A calculator cannot evaluate shape factors such as top fullness, root width, projection, or cup height. That is why trying a couple of nearby sizes is normal and recommended.

Useful tip: check sister sizes. If the band feels too tight but cup volume is right, go up one band and down one cup (for example, 32F to 34E). If the band feels loose, do the reverse.

Quick fit checklist after you calculate

• Band: sits level and feels firm on the loosest hook when new.
• Gore: center panel lies flat against the chest (for wired bras).
• Cups: no gaping and no overflow/spillage.
• Straps: supportive but not digging; most support should come from the band.
• Comfort: no painful pinching, rubbing, or sliding.

Frequently asked questions

Is this calculator UK-specific?

Yes. The output uses UK cup progression (including DD, FF, GG, etc.).

Can I use centimetres?

Absolutely. The tool accepts cm and converts behind the scenes before calculating.

Is this the same as a professional fitting?

No. It is a convenient estimate. A trained in-person fitting can improve precision, especially if you have had recent body changes.

How often should I re-measure?

Any time your body changes noticeably, or every 6 to 12 months as a general check.

Final note

This bust size calculator UK page is designed to give you a reliable first size, save shopping time, and help you understand UK bra labels more confidently. Start with your estimate, try nearby sister sizes, and prioritize comfort and support.