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Are you ready to find your perfect fit? Simply click the 'What size should I get?' button on any product page, answer a few simple questions. Once completed, your best-fit size will be pre-selected for all our products as you continue to shop. 🎉

Now, remember—everyone's unique, and preferences, along with the human body, are more dynamic than any size chart or quiz could ever capture. That being said, our sizing quiz is the next best thing to actually trying on our suits in person 😉🔍 

Every product may fit differently, so keep an eye out for any specific recommendations tailored to certain styles. We want you to feel confident and comfortable in your swim! 

Disclaimer: While we strive to provide the most accurate sizing guidance possible, please note that individual fit preferences and proportions may (read: WILL) vary. Buying the size that the size quiz suggests does not guarantee your fit.

If you have any further questions or concerns, our dedicated customer support team is always here to assist you...and, we offer 1 free courtesy exchange on eligible orders for domestic customers! Happy shopping! 🛍️💕

XXS 00 30 -31 22-23 33-34
XS 0 32 - 33 24 - 25 35 - 36
S 2-4 34 - 35 26 - 27 37 - 38
M 6-8 36 - 37 28 - 29 39 - 40
L 10-12 38 - 39 30 - 31 41 - 42
XL 14-16 39 - 41 32 - 34 43 - 45
2X 18-20 42 - 44 35 - 37 46 - 49
3X 22-24 45 - 48 38 - 41 50 - 52
4X 26-28 49 - 52 42 - 45 53 - 55

When sized and stretched properly, onewith will NOT dig in. Remember: you're a human being, and bodies are so much more dynamic than just numbers on a size chart. DM us if you want further guidance on best size!

NOTE: Do NOT expect our suits to be IDENTICAL to no-show underwear in fit. Do note that our suits do not have the same amount of stretchiness of standard no-show panty due to the inner grip strip & bonding.

Each product page features a fit note to help you choose your best size for that particular style if you find yourself in-between sizes 😊

Looking for cup sizes? We don't size by cup! Go with the measurement of the fullest part of your bust, and reference the Bust section of the chart. Or, shortcut alert 📣 order the same size you would for a camisole!

Some IRL size reference pics for you:

how does onewith run

plus size flattering swimwear

midsize swimwear


onewith swim size reference

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

please don't 🫠🫠🫠🫠 here's why.

⛔ Bracketing + high-quantity first orders are STRONGLY 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/suit you creates inventory issues for us as a small business, and also compromises hygiene best practices. We encourage conscious consumerism by way of small, mindful first orders of 1-2 units. While we naturally love when you stock up on your fave swim once you know your best onewith size, please do so mindfully for our other customers' sake (that is, without the intention of returning extra sizes/styles). While this may be more permissible for an enterprise-level company, we ask that you consider how bracketing + large returns affect a small business, its customers, and the environment. Returns of 3 or more pieces/customer will be subject to a processing fee of $15.95 in addition to the return fee.

Bellows One Piece Torso Measurements

SIZE INCHES - shoulder to crotch, relaxed
XS 24.25
S 25
M 26.75
L 27.25
XL 28
2X 28.75
3X 30.75
4X 31.25