What you need
- The bra you wear most, with its size label still readable.
- A mirror.
- For the later steps, a shop with a fitting room or an online order with free returns.
Use a bra that is not worn out. A stretched band will mislead you in step 1. If your bras are all old, fasten on the tightest hook for the checks and allow for it.
Step 1: test the band
Put the bra on, fastened on the loosest hook, and scoop and swoop. Then:
- Look side-on. Is the band level, or higher at the back?
- Pull the band away from your spine. Does it stretch more than about two inches?
- Slip the straps off your shoulders. Does the bra stay up?
| Result | Band verdict |
|---|---|
| Rides up, pulls away easily, or drops without straps | Too big: go down one band |
| Level, firm, stays put | Correct |
| Painful or hard to breathe on the loosest hook | Possibly too small: check the cups before deciding |
Step 2: test the cups
- Top edge: does it cut in and make a ridge, lie flat, or stand away from you?
- Centre panel: is it touching your breastbone?
- Wires at the side: are they on rib, or on soft tissue?
| Result | Cup verdict |
|---|---|
| Ridge or bulge, centre panel floating, wire on tissue | Too small: go up one cup |
| Flat edge, centre panel touching, wires on ribs | Correct |
| Loose or wrinkled all over, centre panel flat | Too big: go down one cup |
Step 3: work out the next size to try
Apply the band change first. Each time the band goes down one size, the cup letter must go up one just to keep the same volume, and the reverse when the band goes up. Then apply the cup verdict on top.
| Starting from 36C | Try next | Why |
|---|---|---|
| Band too big, cups correct | 34D | Band down, letter up to hold the volume |
| Band too big, cups too small | 34DD | Band down (34D), then one more cup |
| Band correct, cups too small | 36D | Cup up only |
| Band correct, cups too big | 36B | Cup down only |
| Band too small, cups correct | 38B | Band up, letter down to hold the volume |
Remember the UK cup order when you move: A, B, C, D, DD, E, F, FF, G. The sister size calculator will do the band-and-cup swap for any size.
Step 4: try it and repeat
Try the new size and run steps 1 and 2 again. Keep going until both the band and the cups pass. Take the neighbouring sizes into the fitting room with you to save trips.
A common path for someone who has always worn a size bought by guesswork looks like this: 36C, where the band rides up and the cups are slightly small. Then 34DD, where the band is better but still loose and the cups are now right. Then 32E, which passes. Two bands down and one real cup size up is a very typical correction.
When to stop and measure instead
If you have moved more than two sizes in any direction and still fail the checks, you are probably a long way from your size, and measuring will be quicker. A piece of string and a ruler is enough: see how to measure without a tape measure.
When a bra passes, confirm it with the full five-point fit check, including the movement tests.
Frequently asked questions
Can I really find my size without measuring at all?
Yes, if you have a bra to start from and somewhere to try others on. Fitters who work by eye do exactly this: they begin with a size, look at how it fits, and adjust. It takes more try-ons than measuring first.
What if none of my bras fit well?
Use the least bad one. The method works from any starting size, because each check tells you which direction to move. If your current size is a long way out, expect three or four rounds.
Is this more or less accurate than a tape measure?
The end result is more reliable, because you finish with a bra that has passed a fit check. A tape measure simply gets you to that point with fewer attempts, which is why doing both is the quickest route.
Not measured recently? It takes two minutes.
Open the bra size calculator →