Your bra size is two things: a band size, the number, which is the measurement around your ribcage, and a cup size, the letter, which describes the difference between your band and your bust. Measuring at home gives you a good starting point. The fit of the actual bra on your body is what decides whether that size is right.
Sizes also change over time with weight, pregnancy, hormones, exercise and age, so it is worth measuring again at least once a year, or whenever your bras start to feel different.
How to measure at home
You need a soft tape measure, a mirror and either a non padded bra or bare skin.
- Band: wrap the tape snugly around your ribcage directly under your bust. Keep it level all the way round; check in the mirror. Note the measurement in inches. If it is an odd number, round up to the next even number.
- Bust: measure around the fullest part of your bust, keeping the tape level and loose enough not to squash.
- Difference: subtract the band from the bust. Each inch is one cup size.
| Difference (inches) | UK cup |
|---|---|
| 1 | A |
| 2 | B |
| 3 | C |
| 4 | D |
| 5 | DD |
| 6 | E |
| 7 | F |
| 8 | FF |
| 9 | G |
For example, a 34 inch band and a 38 inch bust give a difference of 4 inches: 34D. UK cups continue GG, H, HH, J and so on. US sizes use different letters above D, so check which system a brand uses. Treat the result as a starting point and compare it with the brand’s own size chart.
Checking the fit
Fasten a new bra on the loosest hook, as the band will stretch with wear. Adjust the straps, lean forward and scoop the breast tissue into each cup, then check:
- Band: sits level all the way round and does not ride up at the back. It should feel firm; the band, not the straps, does most of the supporting.
- Cups: hold all the breast tissue without spilling over the top, sides or centre, and without gaping or wrinkling.
- Centre: the front piece between the cups (the centre gore) lies flat against your breastbone in underwired styles.
- Underwire: sits behind the breast tissue, not on it, at the sides.
- Straps: stay put without digging into your shoulders. Straps that dig in usually mean the band is too loose.
Common fit problems
| Problem | Likely fix |
|---|---|
| Band rides up at the back | Go down a band size, up a cup |
| Cups overflow at the top or sides | Go up a cup size |
| Cups gape or wrinkle | Go down a cup, or try a different style |
| Centre does not lie flat | Usually cups too small; go up a cup |
| Straps dig in | Band too loose, or straps too tight |
Sister sizes
When you change the band, the cup volume changes with it. Going down one band size and up one cup keeps roughly the same cup volume: 34C, 32D and 36B are sister sizes. This helps when your size is out of stock or a style runs tight in the band. It is not a replacement for your actual size, but it explains why a “bigger” cup letter is not necessarily bigger.
Styles for different outfits
- Plunge: low centre, suits V necks and low cut tops.
- Balcony or balconette: wider set straps and a horizontal top edge, suits square and scoop necklines.
- Full cup: more coverage and support, good for everyday wear.
- Wireless or soft cup: no underwire, comfortable for lounging and long days.
- Strapless and multiway: for off the shoulder and halterneck dresses; a firm band matters most.
The bras range includes plunge, balcony and wireless styles in many band and cup sizes, often with matching briefs. For special outfits, see bodies and the wider lingerie section. If you are choosing underwear for a particular dress, the guide to choosing a party dress covers necklines and lengths.
Caring for your bras
- Hand wash in cool water, or machine wash on a delicate cycle in a mesh bag, with hooks fastened.
- Do not tumble dry; heat damages elastic and underwires.
- Reshape the cups and dry flat or over a line by the centre.
- Rotate bras so each one rests between wears; elastic recovers better.
While you are measuring, it is a good moment for breast awareness. If you notice a lump, a change in shape or skin, or anything unusual, see your GP.
Quick checklist
- Measure under the bust and around the fullest part.
- Work out the difference to find your cup letter.
- Check the brand’s chart and whether it uses UK or US cups.
- Fasten new bras on the loosest hook.
- Check band, cups, centre, underwire and straps.
- Use sister sizes when a style is tight or out of stock.
- Measure again once a year or after body changes.
Common questions
How often should I measure my bra size?
At least once a year, and again after weight changes, pregnancy, breastfeeding, menopause or a change in exercise routine.
Why do I need a different size in different brands?
Brands use different patterns and size charts, and styles such as plunge and balcony shape the cups differently. Use your measured size as a starting point and judge each bra on fit.
Is DD the same as E?
No. In UK sizing DD comes between D and E, so a DD is one cup smaller than an E. US brands use DDD instead of E, which is why checking the sizing system matters.
