How to measure a swimsuit
Every point, drawn on the garment so there is no guessing where the tape goes.
Quick answer
Lay the one-piece flat and relaxed, then measure five points: chest, hip, length, width and leg opening, in fit-impact order. Swim fabric stretches, so chest is read across the front unstretched, the relaxed reading most listings skip. Hover or tap each step on the diagram to see where the tape sits. Sizely turns those numbers into a chart buyers trust.
A buyer comparing your one-piece to one they own checks chest and hip first, then length to judge torso fit, and there are five points worth listing. Most swim listings show two and call it done. Swimsuits carry negative ease, cut smaller than the body so the fabric stretches to fit, which means a flat number reads smaller than the body it fits. This page draws every point on the relaxed garment, so your reading matches what the buyer measures at home.
- A
Chest
The fit-decider, so it leads. Across the front of the bust panel with the suit flat and the elastic relaxed. Tap this step to see the exact line, and resist stretching the fabric to a number that flatters the listing but fails the buyer.Double it for the full chest circumference, then note that stretch adds reach beyond that.
- B
Hip
Across the widest part of the lower body of the suit, flat and relaxed. This sets whether the seat and hip sit smoothly or dig in, the second thing a buyer checks after chest.Double it for the full hip circumference.
- C
Length
A single vertical run from the shoulder strap top down through the crotch gusset. Tap the step to see where the line starts and ends, since torso length decides whether a one-piece pulls down on the shoulders.Recorded as-is. Do not double.
- D
Width
The width across a defined panel, such as the front at the waist line. It tells a buyer how much the suit covers side to side before any stretch.Recorded as-is. Do not double.
- E
Opening
The leg opening, measured across the edge where the thigh passes through. A narrow opening reads high-cut and snug; a wider one sits lower on the leg.Recorded as-is. Do not double; it is the flat edge of the opening, not a loop around the thigh.
Measure flat and relaxed, never stretched. Smooth the suit out and let the elastic settle to its natural length before the tape touches it, because a swimsuit is built with negative ease and any pull inflates the number. Chest and hip are across measurements that double to a body circumference; length, width and the leg opening are single runs recorded exactly as measured.
Swimsuit size reference
| Size | Chest | Hip | Length | Width |
|---|---|---|---|---|
| XS | 14 | 15 | 24 | 10 |
| S | 15 | 16 | 25 | 10.5 |
| M | 16 | 17 | 26 | 11 |
| L | 17.5 | 18.5 | 27 | 12 |
| XL | 19 | 20 | 28 | 13 |
Frequently asked
Should I measure a swimsuit stretched or relaxed?
Relaxed, always. Swim fabric has a lot of give, so a stretched reading tells the buyer nothing reliable. Lay the suit flat, let the elastic settle to its natural resting length, and take every measurement from there. The buyer doing the same with a suit they own will land on the same numbers, which is the whole point of a chart.
Why is the swimsuit flat measurement smaller than my body?
Swimsuits are cut with negative ease, meaning the pattern is smaller than the body and the fabric stretches to fit. So a flat chest of 16 inches, doubled to 32, can comfortably fit a body chest several inches larger. List the relaxed flat number and let buyers compare it to a suit they already own rather than to a body tape.
Do I double the chest measurement on a one-piece?
For the body circumference, yes, double the chest and the hip since both are taken across one flat layer. Length, width and the leg opening are single runs, so the flat number is already the real number. For the chart itself, most sellers list the relaxed flat number because a buyer can verify it against their own suit.
How do I measure swimsuit length on a one-piece?
Run the tape from the top of the shoulder strap straight down the front and through the crotch gusset, keeping the suit flat and relaxed. This torso length decides whether the suit tugs at the shoulders on a longer body. Hover or tap the length step on the diagram to see exactly where the line starts and ends.
What size swimsuit am I in different countries?
Swim sizing shifts a lot between US, UK and EU labels, so a medium in one brand can be a different number elsewhere. For the full conversion across regions, see our women's international size chart. For listings, pairing that with your own flat measurements removes the guesswork for an overseas buyer.
Should I measure a swimsuit in inches or centimeters?
Either works as long as you stay consistent and label the unit clearly. Swim buyers shop globally, so showing both helps, since one market thinks in inches and another in centimeters. Sizely lists both on every chart so no buyer has to convert a relaxed measurement in their head.
Related size charts & tools
Women's international size chart
Men's international size chartSources: Sizely garment engine, spec #84 (Swimsuit), five named measurement points. ISO 8559 body-measurement standard (representative ranges only). Last verified June 2026.
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