Bra Size Calculator UK NHS

This independent UK bra size calculator gives a starting size from your underbust and full-bust measurements. Bra sizing varies between brands and styles, so always check the fit when you try a bra on.

UK bra size calculator

How to measure your bra size

Measure snugly around your ribcage directly under the bust, keeping the tape level. Then measure around the fullest part of the bust without pulling the tape tightly. You can enter inches or centimetres above.

How the estimate works

The calculator converts centimetres to inches when needed, estimates the nearest even UK band and maps the bust-to-band difference through UK cup progression. Retail calculators commonly use underbust and bust as the two main inputs, but fitting methods differ.

NHS bra-fitting guidance

Frimley Health NHS Foundation Trust provides a traditional measurement method and stresses that professional measurement is the best way to confirm size. Other NHS guidance also notes that bra-size formulae are not always reliable and that fit can vary between makes. For that reason, this calculator is a starting estimate rather than a medical or guaranteed fitting result.

How to check the fit

  • The band should feel firm and remain level rather than riding up.
  • The cups should contain the breast tissue without obvious spilling or gaping.
  • Straps should support without digging into the shoulders.
  • If the bra has wires, they should sit comfortably rather than digging into breast tissue.

Worked example

If the underbust is about 32 inches and the full bust is about 36 inches, the calculator uses a 32-inch band and an approximately 4-inch difference as a starting point. Always try the suggested size and nearby sizes because brands and styles vary.

When should I measure again?

Bra size can change with pregnancy, weight gain or loss, hormonal changes and menopause. Re-measure if your current bras begin riding up, digging in, gaping or spilling.

Limitations

There is no single universal bra-sizing formula. Different retailers and manufacturers may calculate or label sizes differently. Post-surgery or specialist bras may also require individual clinical or professional fitting advice.

Authoritative sources

Related calculators

NHS Calculator · BMI Calculator NHS · How Much Weight Have I Lost Calculator NHS · NHS Pregnancy Calculator · Ovulation Calculator NHS · Biological Age Calculator NHS

FAQs

Is this an official NHS bra size calculator?

No. This is an independent calculator using general UK sizing conventions and NHS fitting guidance.

Are bra calculator results exact?

No. Treat the result as a starting size. Brand, style, breast shape and fitting method can change the best fit.

Should I use inches or centimetres?

Either. The calculator converts centimetres internally before estimating a UK size.

What if the suggested bra does not fit?

Try nearby sizes and check the retailer’s size chart, or ask a trained bra fitter for help.

Disclaimer: This tool is for general fitting information only and is not medical advice or an NHS service.

Scroll to Top