Swimsuit Sizes, Tankinis and UPF, Explained
Swimsuits are sized by bust, waist and hip, a tankini pairs a tank top with a bikini bottom, and UPF 50 fabric lets through about 1/50 of the sun's UV.
By Elliana SmithContributing writer.
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The short answer
Swimsuit sizes come from body measurements: bust, waist and hips, and for one-piece suits often torso length too. Measure yourself, then read the brand's chart for the style you want, because swim charts differ by brand and even by product line.
How to measure for a swimsuit
Keep the tape level and close to the body:
- Bust: around the fullest part.
- Waist: around the narrowest point, where your body bends side to side.
- Hips: around the fullest part.
- Torso: from the high point of the shoulder, down over the bust, between the legs and up the back to the starting point. Charts list it for one-piece suits.
Swimsuit size chart
Nike's women's training swimsuits use numbered sizes. A few rows from its chart, in inches:
| Size | Bust | Waist | Hip | Torso |
|---|---|---|---|---|
| 28 | 32.5 to 34.5 | 25.5 to 27 | 35 to 36.75 | 58.75 to 60.5 |
| 30 | 34.5 to 36.5 | 27 to 28.5 | 36.75 to 38.5 | 60.5 to 62.25 |
| 32 | 36.5 to 38.5 | 28.5 to 30 | 38.5 to 40 | 62.25 to 64 |
| 34 | 38.5 to 40.5 | 30 to 31.5 | 40 to 41.5 | 64 to 65.75 |
| 36 | 40.5 to 42.5 | 31.5 to 33 | 41.5 to 43 | 65.75 to 67.5 |
The full chart runs from size 26 to 42. Nike says these suits are cut to compress, to cut drag in the water, and suggests sizing up for a looser fit. Other brands and other swim lines use their own size names and ranges, so always open the chart for the exact suit.
What is a tankini
A tankini is a two-piece swimsuit: a tank top paired with a bikini bottom. The top reaches from just above the navel to the top of the hips. US designer Anne Cole is credited with launching it in 1998, and the name joins "tank top" with "bikini."
The top is what sets it apart from a classic bikini. Some people see it as one-piece coverage with two-piece convenience: you do not have to take off the whole suit for a bathroom break.
What UPF means in swimwear
UPF stands for Ultraviolet Protection Factor. It tells you how much of the sun's UV radiation (UVA and UVB) a fabric lets through. The Skin Cancer Foundation explains it like this:
- UPF 50 blocks 98% of UV rays and lets 2%, or 1/50, through.
- UPF 30 to 49 counts as very good protection; UPF 50+ as excellent.
- Its Seal of Recommendation needs UPF 50.
Swimwear tests fabric hard. Wet fabric can lose protection, and stretched fabric lets more UV through as the fibers pull apart, so a tight suit protects less than the same fabric worn loose. Dark or bright colors absorb more UV than pale ones.
How we count
Colors in the chart are read from each swimwear listing's store data on Wiki Shopping on October 26, 2026. Of the 268 swimwear listings that day, the chart shows the colors with the most listings. Counts change as listings are added or removed. Browse the range from clothing, shoes and jewelry.