SIZE GUIDE

Swimwear is the hardest garment to buy online and the one people most often get wrong. It is cut close, it behaves differently wet, and its sizing does not map cleanly onto the dress size you know. This guide covers how to measure yourself, how to read a size chart, and what to do when you fall between sizes.

How to take your measurements

Use a soft tape measure, stand relaxed and upright, and wear a soft unstructured bra — a padded or heavily wired bra changes the bust measurement enough to put you in the wrong size. Keep the tape level all the way round and slide a finger between the tape and your body, so the number you write down leaves room to breathe rather than recording you at full compression.

• Bust — around the fullest part, tape level under the arms and across the shoulder blades.
• Underbust — directly beneath the bust, snug but not tight. This is the measurement that decides support in a bikini top.
• Waist — the narrowest part of the torso, usually just above the navel. Do not hold your stomach in.
• Hips — around the fullest part of the hips and seat, feet together.
• Torso length — from the top of the shoulder, down the front through the crotch and back up to the same shoulder point. This is the one almost everyone skips, and it is the reason one-pieces dig in.

Reading a size chart

Almost every brand publishes body measurements rather than garment measurements — that is, the size of the person the garment is designed to fit, not the flat dimensions of the fabric. Swimwear is engineered with negative ease, meaning the garment is deliberately smaller than the body and stretches to fit. This is why the flat measurement of a swimsuit looks alarmingly small and why comparing it to a t-shirt is meaningless.

Where your measurements straddle two sizes, follow the largest one for the part of the garment that has to hold: bust and underbust for a top, hips for a bottom, torso length for a one-piece. A bottom that is slightly generous rides comfortably; a top that is slightly small does not.

Swimwear versus everyday sizing

Two rules cover most cases. Non-stretch essentials — linen shirts, cover-ups, kaftans — generally run true to size, so take the size you normally wear. Swimwear knitted in a double-layer fabric behaves differently: the second layer removes some of the stretch, so if you are between sizes in a double-lined suit, size up. Single-layer swimwear stretches more and can usually be taken in your true size.

The one-piece problem

A one-piece has to fit three measurements at once — bust, hips and the vertical distance between them — and torso length varies far more between people than either of the other two. A suit that fits in the bust and hips but pulls uncomfortably at the shoulders or crotch is almost always a torso-length mismatch rather than a size problem, and going up a size makes the garment loose everywhere else without adding much length. Where a brand offers a long-torso option, that is the answer; where it does not, a two-piece will fit better.

Fit checks before you commit

1. Raise both arms above your head. Straps should not gape at the front or slide off the shoulder.
2. Bend forward from the waist. A scoop or open back should stay where it is.
3. Sit down. Leg openings should follow the crease of the hip rather than cutting across the thigh.
4. Run a finger under every elastic edge. It should slide easily; if it does not, the suit will mark you after an hour.
5. Check the lining against the light. A double-lined body will not go translucent when wet; a single-lined one may.

Adaptive and post-surgery fit

A growing number of swimwear makers will alter garments for wearers with a prosthetic limb or other physical disability, and will sew in pockets for prosthesis wearers after breast cancer surgery. This is often not advertised on the product page and is worth asking about directly before ordering; where it is offered, it is usually free. Pocketed swimwear designed for a breast form is also available as standard from specialist retailers, and fits differently from an ordinary suit — the front lining is heavier and the neckline higher.

If it arrives and it is wrong

Try it on over underwear, on a dry body, in good light, and keep the hygiene strip in place until you are sure. Almost every retailer voids a swimwear return if that strip has been removed, and once it is gone the item genuinely cannot be resold. Returns terms for swimwear are stricter than for other clothing for exactly this reason, and they are set by the retailer you bought from.