Swimsuit sizes: bust, underbust, waist and hips

Measure your bust, underbust, waist and hips, find them in the chart, and go by the measurement that matters most for the piece: the hips for a one-piece or a bottom, the bust and underbust for a top. Between two sizes, the larger one.

The tables are copied from Ruban Size's Swimwear template, typical values that each store replaces with its own, with inches added (2.54 cm to the inch). A brand's own chart wins over this one.

Swimsuit size chart

The same measurements in inches:

How to measure for a swimsuit

The template's four steps, in a swimsuit or light underwear:

1. Bust: around the fullest part of your bust, tape level.
2. Underbust: snugly around your ribcage, just under the bust.
3. Waist: around your natural waistline, the narrowest part of your torso.
4. Hips: feet together, around the fullest part of your hips.

How to read it

1. Find each measurement in its row. If they all land in one size, that's your size.
2. If they disagree, go by the piece. A one-piece has to fit everywhere, so the largest size wins. A bikini bottom goes by the hips and waist, a top by the bust and underbust.
3. Between two sizes, take the larger one. That is the template's own fit note.
4. Read your number in the system you know: an M is a US 8 to 10 and an EU 40 to 42.

Why swimsuits run close

The Swimwear template sits one step toward "Runs slightly small" on the fit scale, with this note for shoppers: "Swim fabrics are designed to fit close: between two sizes, take the larger one."

The numbers show it too. Put the Swimwear template beside the Dresses template and every swim range, bust, waist and hips, sits 2 cm lower at the same letter: a swim M is a bust of 88 to 93 cm, a dress M 90 to 95. The US numbers shift at the ends: the swim XS is a US 2 where the dress XS is 0 to 2, and the swim XL a US 16 where the dress XL is 16 to 18. The waist and hips of the swim chart are the same as those of Ruban Size's Leggings and activewear template, another close fit. More on the dress side in women's clothing sizes compared.

Separates, one-pieces and bra-sized tops

Separates. A body can be one size on top and another below. If you sell bikini tops and bottoms as separate products, give each its chart: the top by bust and underbust, the bottom by waist and hips. Shoppers then buy an M top and an L bottom without guessing.

One-pieces. A one-piece also has to fit the length of the torso, from shoulder to crotch, and the template has no row for it. If your brand gives a torso length, add it as a row.

Bra-sized tops. Underwired tops sold by bra size (34C, 75C) follow a bra chart, by underbust and bust. The systems are in the bra size conversion chart.

How a Shopify store should show swimsuit sizes

1. Four measurements, bust, underbust, waist and hips, with how to take each.
2. US and EU (and UK if you sell there) on rows of their own, marked as size systems.
3. A fit note: how the suit runs, and which way to go between two sizes.
4. One chart per kind of product: tops, bottoms and one-pieces where they differ.
5. Centimeters and inches, with a switch, inches first for US shoppers.

How Ruban Size does it

The Swimwear template has the five sizes above, US and EU rows marked as size systems, the four measurements, and a How to measure block beside a body figure: pointing at a step lights up the measurement in the figure and its row in the table. The fit scale shows shoppers "Runs slightly small" with the note. It opens as a draft and shows nowhere until you save it and choose its products, by type, tag or collection with the display rules.

Find my size reads the chart as swimwear. The hips count most, then the bust, the waist and the underbust. Swim fabric counts as stretch by default, so a measurement a little over a range costs less than it would on a woven dress, and the "Runs slightly small" setting moves the answer up by a fifth of a size step.

A bust of 90 cm, an underbust of 78, a waist of 72 and hips of 98 get "Your size: M", with one line per measurement ("Bust 90 cm: M, middle of the range") and "This item runs small: we took it into account." Hips of 101 cm alone, the top of M in the table, get "You are between M and L. We suggest L." and "M may also fit if you like a closer fit."

A torso row is shown in the guide like any other row, but Find my size doesn't use it: torso length isn't one of its measurements.

Questions

What size swimsuit is a US 8?

An M in Ruban Size's Swimwear template (US 8 to 10, EU 40 to 42), for a bust of 88 to 93 cm and hips of 96 to 101 cm.

Should I size up in swimsuits?

Between two sizes, yes: swim fabrics fit close, as the template's note says. If all your measurements land in one size, take that size.

Are swimsuit sizes the same as dress sizes?

The letters are, the bodies aren't. In Ruban Size's templates, every swim range sits 2 cm below the dress range of the same letter, and the swim XS is a US 2.

How do I measure for a bikini?

Bust and underbust for the top, waist and hips for the bottom, with a soft tape kept level. If the top and bottom are sold separately, choose each from its own chart.