Size Guide

size chart

Size		Bust
XXS	00	30.5 - 32
XS	0	32 - 33.5
S	2-4	33.5 - 35
M	6-8	35 - 37
L	10-12	37 - 39
XL	14-16	39 - 41.5
2XL	18-20	41.5 - 44
3XL	22-24	44 - 47

Size		Waist	Hips
XXS	00	23 - 24.5	33 - 34.5
XS	0	24.5 - 26	34.5 - 36
S	2-4	26 - 27.5	36 - 37.5
M	6-8	27.5 - 29.5	37.5 - 39.5
L	10-12	29.5 - 31.5	39.5 - 41.5
XL	14-16	31.5 - 34.5	41.5 - 44
2XL	18-20	34.5 - 37.5	44 - 47
3XL	22-24	37.5 - 41	47 - 50.5

Size		Bust	Waist	Hips
XXS	00	30.5 - 32	23 - 24.5	33 - 34.5
XS	0	32 - 33.5	24.5 - 26	34.5 - 36
S	2-4	33.5 - 35	26 - 27.5	36 - 37.5
M	6-8	35 - 37	27.5 - 29.5	37.5 - 39.5
L	10-12	37 - 39	29.5 - 31.5	39.5 - 41.5
XL	14-16	39 - 41.5	31.5 - 34.5	41.5 - 44
2XL	18-20	41.5 - 44	34.5 - 37.5	44 - 47
3XL	22-24	44 - 47	37.5 - 41	47 - 50.5

onewith size quiz

everyone’s unique, and no quiz can capture every preference or body type — but this is the next best thing to trying on in person.

disclaimer: results are a guide, not a guarantee. fit preferences may vary.

1 FREE exchange on eligible US orders

size inclusive (XXS-3XL)

patented, US Patent No. 12,357,039

See it in your size

Woman in a black onewith bikini sitting on rocks by the ocean — andrypena / XXS + XXS

Woman in a red onewith one piece swimsuit standing on a boat with blue water in the background — kareenasinghh / XS

Woman wearing a blue onewith bikini — kareenasinghh / XS + XS

Woman in a red onewith one piece swimsuit standing on a boardwalk with greenery in the background — carolyn.mhickman / S

Woman wearing a blue onewith bikini standing against a wooden wall. — dayj.doll / S + S

Woman wearing a blue onewith bikini top in a pool — megdlyn / S

Woman in a blue onewith bikini and sunglasses standing on a balcony with a view of a marina — ivana_ferro / S + M

Woman in a black onewith bikini standing on a beach — alyssa.models / S + M

onewith founder Hayley wearing a onewith black one piece swimsuit taking a mirror selfie — onewithswim / S

Woman in a black onewith one piece swimsuit standing on a beach with water in the background — ahmeimae / S

Woman wearing a black onewith one piece swimsuit in front of the ocean — ahmeimae / S

Woman wearing a black bikini on a beach — alexhakim16 / S + M

Woman in a black onewith bikini standing on a beach with water and sky in the background — ahmeimae / S + M

Woman wearing a brown onewith bikini with a bag — onewithswim / S + S

Woman in a onewith bikini and hat on a beach at sunset — carolyn.mhickman / S + S

Woman in a black onewith bikini and hat standing in the ocean — emily_shultis / S

Woman in a black onewith bikini posing by a pool — traceydoes_ / S + M

Woman wearing a blue onewith bikini taking a mirror selfie — onewithswim / S + S

Woman wearing a black onewith bikini taking a selfie — lordnavji / M + M

Woman in a blue onewith bikini standing on a dock by water — ahmeimae / M + M

Woman in a black onewith bikini standing against a teal door. — Anaidayl / M + M

Woman in a black onewith bikini — ahmeimae / M

Woman in a blue onewith bikini and pink hat by a pool — ivana_ferro / S + M

Woman in a black onewith bikini sitting on a beach with ocean in the background — alyssa.models / S + M

Woman in a black onewith bikini sitting on a counter — anaidalyramos / M + M

Woman in a black onewith bikini on a boat — ivana_ferro / S + M

Woman in a red onewith one piece swimsuit standing by the ocean — ashleyyharveyy / L

Woman sitting on a dock by a body of water wearing sunglasses and a black onewith bikini top. — ceciliakauffmanharris / L

Woman wearing a black onewith bikini standing on a beach — chloewoz / XL

Woman in a blue onewith bikini standing in a pool with a flower in her hair — summerleilani_ / XL

Woman wearing a black onewith bikini standing on a balcony. — chloewoz / XL + XL

Woman wearing a black onewith bikini set — chloewoz / XL + XL

Woman wearing a black onewith bikini standing on a balcony overlooking a beach with palm trees. — wendyfrita / 2XL + XL

Woman wearing a black onewith one piece swimsuit in a pool — gracedotymusic / 2XL

Woman in a blue onewith bikini holding a drink under a palm tree — cheyenneolson / 2XL

Woman wearing a black onewith one piece swimsuit taking a mirror selfie. — gracedotymusic / 2XL

Woman wearing a black onewith bikini sitting on a stool indoors. — gracedotymusic / 2XL + 2XL

Woman in a blue onewith bikini standing on a boat with rocky cliffs and blue water in the background — Marisa / 2XL + 2XL

Woman in a black onewith bikini standing on a rocky beach with houses and trees in the background. — tatumblinncoffey / 3XL + 3XL

Woman wearing a black onewith bikini standing on a beach with ocean in the background — misscurvygirl_love / 2XL + 3XL

Woman in a black onewith bikini standing on a sandy beach with water and boats in the background. — ariellamayamendes / 2XL + 3XL

image of model wearing onewith swim bottoms next to a model wearing a non-onewith swim bottom

important info for when you get your onewith

how to warm up your onewith

this is swimwear unlike anything else on the market, so with that, it has some special instructions to truly get a fit that's onewith your body ✨ 'warming up your onewith’ (aka giving the garment a stretch) is MISSION-CRITICAL to the fits-like-undies vibe. your swim actually SHOULD dig in a bit to start if it’s your proper size. then, with a stretch at the openings, it should fit and feel smooth, like a second skin (and/or your fave seamless undies) 🫧

what to know about sizing

can I just order a few sizes and styles and return what doesn't fit?

⛔ Bracketing/high-quantity first orders are discouraged: while we understand the desire to find your best size(s) and styles, ordering multiple variants of a piece with the intention of returning those that do not fit creates inventory issues for us as a small business, and also compromises hygiene best practices. We encourage conscious consumerism by way of mindful first orders of 2 styles.

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