Bra size guide

Wearing the right bra size is essential for comfort, support and confidence. However, bra sizing can vary across brands and regions, making it important to know how to measure yourself correctly. Our bra size guide will help you determine your perfect fit with a step-by-step measurements, a detailed size chart and useful tips for choosing the right style.

How to measure your bra size 

You can measure your bra size at home by following these simple steps:

A tape measure is required.

1.     Measure your band (over bust measurement)

Stand upright without a bra on, and wrap the tape snugly under your bust. Take your measurement in inches. If you land at an even number, that is your band size. If it’s an odd number, round up to the nearest inch.

2.     Measure your bust (under bust measurement)

Wrap the tape around the fullest part of your bust and take the measurement in inches. Round to the nearest inch if required.

3.     Find your cup size

For this part, subtract your band size with your bust measurement. The total will determine your cup size and letter below:

0=AA

1=A

2=B

3=C

4=D

5=DD

6=F

7=FF

8=G

9=GG

10=H

11=HH

12=J

13=JJ

14=K

4.      Confirming your size

Combine your band and cup size, so you have a number followed by a letter. Example, 34B.

Bra size chart

 Disclaimer: the following chart is for reference only. The fit of the garment may vary depending on the style, cut and fabric. 

Bras fits and styles:

At Primark, we offer a wide range of bras to suit different body shapes, support needs and outfits. Here’s a breakdown of our popular styles. 

T-shirt bras 

A classic everyday bra that lightly contours and features minimal detailing.

Balcony bras

Includes lower-cut cups with wide-set straps for a lifted, flattering shape. Ideal for low or sweetheart necklines. 

Sports bras 

Designed for impact support during workouts.

Full cup bras

Especially good for larger busts, full cup bras offer all over coverage, full support and suits all bust shapes.

Push-up bras 

Adds volume and enhances cleavage with padded cups. 

Plunge bras

Features a deep V-cut for low-cut tops and dresses.

Bralettes 

Soft, wire-free designs, made for lounging or everyday wear.

Strapless and multiway bras

The style might be strapless or offer straps that can be removed or repositioned. Perfect for off-the-shoulder and asymmetric necklines.

FAQs 

How do I know if my bra fits correctly? 

A well-fitting bra should sit firmly and comfortably on your body. Here’s how to check:

1. The band should be snug, not restricting. If it rides up, it’s too loose. If it digs into your skin, it’s too tight.

2. Your breasts should sit comfortably inside the cups with no overflow or gaps.

3. The straps should sit comfortably on your shoulders without slipping or leaving marks.

4. The underwire should sit flat against your chest.

How often should I measure my bra size? 

You should measure your bra size every 6 to 12 months, or whenever you notice a change in the fit.

How do I work out my UK bra size? 

Follow our how to measure your bra size steps and bra size conversion chart above to find your UK size. 

Which cup size is bigger, B or C or D? 

Cup size increases as you move along the alphabet. In this case, D is the biggest, followed by C, then B. This represents the difference between your bust measurement and your band size—the larger the difference, the bigger the cup.

What is the difference between sister sizes?

Sister sizes are alternative bra sizes that share the same cup volume, despite having different back sizes and cup letters. For example, if you wear a 34C, your sister sizes would be:

• One size up: 36B (looser band, same cup volume.)

• One size down: 32D (tighter band, same cup volume.)

Note: Make sure you know your true cup size before trying to work out your sister size.

Bra fitting guides

Finding the perfect fit can make all the difference in comfort and support. Our bra size chart makes it easy to measure yourself at home and discover the best size for your shape. Plus, explore our expert bra fit guides for tips on choosing the right style, how to measure yourself at home, and ensuring a flawless fit. Whether you're looking for bras for small busts, small busts or the most comfortable bras our guides will help you shop with confidence.

• How to measure bra size

• Bra styles guide

• How to choose a sports bra

• Best bras for small busts

• Most comfortable bras