What you need
A soft tailor’s tape, bare skin or thin underwear, and a mirror to check the tape sits level. Without a tape, wrap a shoelace around yourself, mark where it meets, then lay it flat against a ruler.
Bust, waist and hip
- Bust. Around the fullest part of your chest, with the tape level front and back.
- Waist. The narrowest point, usually just above the navel. Breathe out normally first.
- Hip. The widest point around your seat, feet together.
Keep the tape flat against your skin without pulling it. A tape drawn tight reads one to two centimetres small, which is enough to drop you a size.
Torso length for one-pieces
Run the tape from the top of one shoulder, down between your legs, and back up to the same shoulder. Brands rarely print this number, but it explains a suit that fits everywhere except the straps. A long torso pulls the shoulders down and rides the legs up, and no amount of sizing across the bust will fix it.
Reading the chart
Your three numbers will often land on three different sizes. Take the largest one: fabric can take in a measurement that’s too generous, but a suit that’s too small anywhere simply won’t go on. In low-stretch compression fabric, go up again. Then check those numbers against the brand size charts, because a size 32 is not the same garment from one label to the next.
Relevant suits
| Suit | At a glance | Sizes | Price | |
|---|---|---|---|---|
 Nike Nike Mens Hydrastrong Team Colorblock Jammer - Black/White | Chlorine-resistantjammer | 28,30,32,34,36 | $49 £36.96 | Allens Swimwear→ |
AR Arena Arena Women’s V-Back One Piece MaxLife | Chlorine-resistantv-backone piece | 26,28,30,32,34,36 | $54 | Amazon→ |
 Speedo Speedo Womens Print Medalist Swimsuit - Anthracite Grey | Chlorine-resistant | 30,32,34,36,38,40,42 | $50 £37.70 | Allens Swimwear→ |
MI Mizuno Mizuno EXER Women’s Thick Strap Swimsuit | Chlorine-resistantone-piece | 8,10,12,14,16,18,20,22,24,26,28,30,32,34,36,38,40 | $70 | Amazon→ |
 TYR TYR Womens Arterix Cutoutfit Swimsuit - Titanium | Chlorine-resistant | 30,32,34,36 | $62 £46.59 | Allens Swimwear→ |
Prices and exchange rate as of Oct 13, 2026 (£1 = $1.3220). Allens prices are charged in pounds; the dollar figure is a conversion. Check the retailer for the current price.
Find your size
FAQ
Should I measure over a swimsuit?
No. Measure on bare skin or over thin underwear. A swimsuit already compresses you by a centimetre or two, and that’s exactly what makes the chart read wrong.
How often should I measure again?
Whenever your training load or body changes noticeably, and otherwise about once a year. Most people end up in a stale size because they’re working from numbers they took years ago.