Swimsuit Sizing by Style: One-Piece Torso, Bikini Cup and Fit

Which measurement decides each style

Every swimsuit style fits closely at different points. Start here, then use the body-measurement charts in our swimming suit size charts to turn the measurement into a size.

Swimsuit styles and the measurement to size by
Style	Size by	Then check
One-piece	Bust	Torso loop, then hip
Bra-sized bikini top	Band and cup	Strap and tie adjustment
Letter bikini top (S/M/L)	Bust and cup range	Under-bust if a band is sewn in
Classic or low-rise bottom	Hip	Waist if there is no tie
High-waisted bottom	Hip and natural waist	Rise: the waistband should reach the navel or above
Tankini top	Bust	Length; it should reach the bottom's waistband
Swim dress / skirted suit	Bust	Torso loop, as for a one-piece

Separates exist to fix the most common problem: a bust and hip that are different sizes. A 34DD top with a size 6 bottom, or an S top with an L bottom, is an ordinary order.

One-piece swimsuits: torso length

A one-piece runs from your shoulders to your crotch without a break, so its length has to match your torso. Width can stretch; length cannot stretch much without the suit cutting in.

Measure your torso loop. Put the tape on top of one shoulder, halfway between the neck and the shoulder point. Run it down the front over the bust, between the legs and up the back to the starting point.
Compare with the brand's torso figure if it publishes one. Brands that do usually list a range for each size.
Without a brand figure, use common guidance: about 56 in (142 cm) or less is a short torso, 58-62 in (147-157 cm) average, and 62 in (157 cm) or more long. Long-torso and "tall" one-pieces add length to the body for that last group.

Height is a rough proxy only. Women around 5 ft 7 in (170 cm) and taller often need long-torso cuts, but leg length varies, so a 5 ft 4 in woman with a long body can need one too. The same measurement is used for jumpsuits; see jumpsuit sizes.

Torso quick test

Put the suit on and stand straight. Straps should lie flat without pressing into the shoulder, and the leg openings should sit at the crease of the hip. If you lift your arms and the crotch pulls up, the torso is too short; if the fabric wrinkles across the stomach, it is too long.

Bikini tops: bra sizes and letter sizes

Bikini tops come in two systems. Bra-sized tops use a band and cup like a bra and fit best on fuller busts. Letter-sized tops (S, M, L) cover a range of band and cup combinations and suit small to medium cups, since triangle and bandeau styles have little structure.

Bra-sized tops: start from your bra size. Swim tops cannot be loosened with hooks during the day and are pulled on wet, so the band should be firm on the loosest setting.
Letter tops: brands typically design each letter for A-C or B-D cups. If you are DD/E or larger, look for D+ or DD+ lines, or bra-sized tops, rather than going up a letter, which adds band width but little cup depth.
Underwire and molded cups follow bra sizing closely. Triangle tops with sliding cups are forgiving across about two cup sizes.

Bra band and cup conversions for swim tops
US band	UK band	EU band	FR band	AU band
32	32	70	85	10
34	34	75	90	12
36	36	80	95	14
38	38	85	100	16
40	40	90	105	18

Cups match across the US, UK and EU up to D, then split: UK DD is US DD (sometimes written E) and EU E; UK E is US DDD (F) and EU F; UK F is US G and EU G. Swimwear brands from the UK and Australia use UK cups. More on band and cup measuring is in the bra size guide.

Bikini bottoms and high-waisted bottoms

Bottoms are sized by hip, because the seat is the widest point they must cover. If your hip falls between sizes, side-tie bottoms adjust; fixed-side bottoms do not, so take the larger size if you prefer full coverage and the smaller if you want a firm, cheeky fit.

Bikini bottom styles
Style	Rise	Rear coverage	Sizing note
Full / classic	Mid, below the navel	Full	True to size by hip
Hipster / boyshort	Low to mid	Full; boyshorts have short legs	Size by hip; boyshorts can feel tight on thighs
Moderate / cheeky	Low to mid	Partial	Size up if you want more coverage
Brazilian / thong	Low	Minimal	True to size; too small rolls at the sides
High-waisted	At or above the navel	Full	Check hip and waist; long torsos may need a size up for rise

High-waisted bottoms have to cover the distance from the crotch to the natural waist, so they behave like a short one-piece. If your waist is a size larger than your hip, choose by waist so the band does not roll down; if your hip is larger, choose by hip and accept a looser waist.

International swimsuit size conversion

Women's swimwear sizes by country
US	UK	EU / FR	Italy	Australia	Letter
2	6	34	38	6	XS
4	8	36	40	8	S
6	10	38	42	10	S
8	12	40	44	12	M
10	14	42	46	14	M
12	16	44	48	16	L
14	18	46	50	18	L
16	20	48	52	20	XL

German and Scandinavian swim brands often label one step lower than the EU column (EU 38 for a UK 12). Competitive suits use their own numbered sizes, explained in the swimming suit size charts. Full dress-size conversions are on the dress size chart.

Swimsuit fit problems and fixes

Common swimsuit fit problems
Problem	Likely cause	Fix
Straps dig into shoulders	Torso too short	Long-torso cut, or a size up
Fabric bunches at the stomach	Torso too long	Petite cut or a size down
Leg openings ride up	Torso too short or hip too small	Long torso, or size by hip
Cups gap at the top	Cup too large or wrong shape	Smaller cup, or a balconette instead of a plunge
Bust spills at the sides	Cup too small	Bra-sized or D+ top; not a bigger letter
Band rides up the back	Band too loose	Smaller band, larger cup (sister size)
Bottoms roll at the waist	Too small, or waist larger than hip size	Size by waist, or choose a wider band
Suit sags when wet	Too large, or chlorine-damaged elastane	Size down; choose chlorine-resistant polyester for pool use

Chlorine and heat break down elastane over time, which makes a well-fitting suit sag after a season of regular pool swimming. That is a fabric problem, not a sizing one: polyester-rich, chlorine-resistant suits keep their fit much longer if you swim several times a week.

Frequently asked questions

Should a swimsuit be tight or loose?

Snug when dry. Swim fabric stretches and relaxes slightly in water, so a suit that feels comfortable but firm in the fitting room will feel right in the pool. A suit that is loose when dry sags, gaps at the leg and fills with water.

Do I buy my bra size in a bikini top?

For bra-sized tops (32C, 34DD), start with your usual bra size. Swim tops have no hooks to adjust and are pulled on wet, so if you are between band sizes, the tighter band usually stays in place better. For letter-sized tops, check the cup range the brand lists for each letter.

How do I know if I need a long torso swimsuit?

Measure your torso loop. Brand guidance commonly puts average torsos at about 58-62 in and long torsos at about 62 in and over. Other signs: straps dig into your shoulders, the leg openings ride up, or the suit pulls down at the neckline when you stand straight.

Are swimsuit sizes the same as clothing sizes?

In the US, mostly yes: a size 8 in dresses is usually a size 8 or medium in swimwear. Swimwear from UK, European and Australian brands uses their own country's dress sizes, so a UK 12 swimsuit is a US 8.

What size swimsuit when pregnant?

Buy maternity swimwear in your pre-pregnancy size; the front panel is cut longer to cover the bump. Regular one-pieces usually become too short in the torso by about 20 weeks. Our maternity size guide covers how the bump grows.