Find Your Bra Size with Privacy
UK Bra Size Calculator
Enter your measurements to get a reliable UK starting size, recommended styles for your breast shape, sister sizes, and international conversions. All calculations happen privately in your browser.
1 Enter Your Measurements
Measure while wearing a thin, non-padded bra. Keep the tape level and parallel to the floor.
2 Select Your Breast Shape (optional but recommended)
Shape affects which bra styles will fit you best. Choose the one that most closely matches your natural shape.
Your Recommended UK Starting Size
This is a reliable starting point. Always try the bra on and check the fit checklist below.
Recommended Bra Styles for Your Shape
Your Sister Sizes 👯♀️
Same cup volume, different band. Useful if the recommended band feels too tight or too loose.
International Size Conversions 🌍
| Region | Band | Cup | Full Size |
|---|
Quick Fit Checklist
- Band sits level and snug (you should fit two fingers underneath).
- Centre gore lies flat against your chest.
- Breasts fill the cups completely — no gaping or spillage.
- Straps stay in place without digging in.
- Underwire follows your natural breast root (no poking).
🔒 100% private — your measurements never leave your browser.
How to Measure Your Bra Size (UK)
You only need two measurements and a soft tape.
1. Underbust (Band)
Wrap the tape snugly around your ribcage, right under your bust. Keep it level and breathe out. This is your band size.
2. Bust (Cup)
Wrap the tape around the fullest part of your bust. Keep it comfortable — not tight.
Enter both numbers in the calculator above. It uses the modern UK method (no old “add 4 inches” rule) and gives you a reliable starting size plus sister sizes.
Quick tips
- Measure over a thin non-padded bra or no bra
- Keep the tape level all the way round
- Always try the size on — brands fit slightly differently
Frequently Asked Questions
Is this calculator accurate?
It gives a strong starting size using modern fitting methods. Always try the bra on and check the fit (band level, cups full, centre gore flat).
Why is my new size different from what I wear now?
Most women wear a band that is too big and a cup that is too small. A smaller band with a larger cup often feels much more supportive.
Should I measure with a bra on?
Yes — wear a thin, non-padded bra. Padded or push-up bras will make the bust measurement too big.
What are sister sizes?
Sister sizes keep the same cup volume but change the band. If the recommended band feels too tight or too loose, try the sister sizes shown by the calculator.
Do all UK brands fit the same?
No. Marks & Spencer, Bravissimo, Panache and others can fit slightly differently. Use the result as your starting point and adjust if needed.
Privacy & About
Everything is calculated in your browser. Your measurements never leave your device — we don’t store or see them.
This free UK Bra Size Calculator was built to give women a simple, honest starting size without outdated charts or complicated steps.
