Swimwear shopping online is frustrating for a simple reason: sizing is inconsistent across brands, measurements don't translate clearly to fit, and the stakes are higher than buying a regular garment — ill-fitting swimwear either restricts movement or fails to stay in place in the water. This guide gives you the practical information to get the right fit the first time.
Why Swimwear Sizing Is Complicated
Unlike dress shirts or trousers, swimwear has no universally adopted sizing standard. A "Medium" from a European brand, an Australian brand, and a Southeast Asian brand can differ by 5–8 cm in chest measurement. Add to that the fact that swimwear is meant to be worn wet, underwater, and in motion — the fit requirements are completely different from casual clothing.
The only reliable approach: use your actual measurements and match them against the specific brand's size chart.
The Three Measurements That Matter
For Women
- Bust: Measure around the fullest part of your chest, keeping the tape parallel to the floor. Don't pull tight — a natural, relaxed measurement.
- Waist: The narrowest point of your torso, typically 2–3 cm above your navel.
- Hips: The fullest part of your hips and seat, typically 20–25 cm below your natural waist.
For swimsuits and rashguards, bust and hips are the most critical. If you're between sizes, size up — swimwear that's too small restricts breathing and movement; sizing up by one step is usually more comfortable in the water.
For Men
- Chest: Around the fullest part of your chest, arms relaxed at sides.
- Waist: Around your natural waist (not where you wear your trousers — usually higher).
For boardshorts, waist measurement is primary. For rashguards, chest measurement governs fit.
For Children
- Height: Most kids' swimwear is sized primarily by height in Southeast Asian sizing conventions.
- Chest and weight: Secondary measurements that help when a child is outside the average proportions for their height.
Children grow quickly — check measurements at each season rather than assuming last year's size still fits.
How Swimwear Should Fit
Rashguards
A properly fitting rashguard should:
- Lie flat against your body without bunching, pulling, or gaping
- Allow full arm movement overhead without the hem riding up
- Stay in place during overhead paddle strokes and duck dives
- Not constrict breathing when fully inhaling
- Cover your lower back when your arms are extended overhead
The fit should be snug but not tight. If you can see skin impressions from the stitching after wearing, it's too tight.
One-Piece Swimsuits
- Straps should sit comfortably on your shoulders without digging in or slipping off
- The bust area should provide support without gaping or overflowing
- The body of the suit should lie flat — no pulling across the bust or hips
- The crotch seam should sit comfortably without cutting in
- When you bend over, the suit should move with your body, not gap away from it
Bikinis / Swim Sets
- Top: Cups should fully contain the bust without spillage or gaping. Underwires (if present) should not dig into breast tissue. Adjustable straps let you customize support level.
- Bottom: Should sit at a comfortable height on your hips. Too small creates visible compression marks; too large creates sagging in the seat.
Boardshorts (Men and Boys)
- Should sit at your natural waist or hip (depending on style preference)
- The drawstring/velcro closure should be able to hold the waist comfortably without overtightening
- Length is preference — knee-length is standard for surfing and water sports, shorter for swimming
- There should be no pulling across the seat when you crouch or squat
Asian vs International Sizing
This is particularly relevant for Southeast Asian shoppers. Many international brands (especially European and US) size for taller, broader body frames. Asian sizing conventions tend to run smaller and are calibrated for shorter torso lengths, narrower shoulders, and different hip-to-waist ratios.
If you're buying from an international brand, adding 1–2 sizes to your usual Asian size is a common adjustment. When in doubt: measure first, then check the specific brand chart.
Sailbee's sizing is calibrated for Southeast Asian body proportions — if you're used to international brands sizing up, you may find you fit your usual measurement size without adjustment.
Swimwear Fabric and Stretch
Most swimwear is made from nylon or polyester blended with elastane (spandex). Higher elastane percentage means more stretch and recovery — good for active water sports. When assessing fit, consider that swimwear stretches noticeably when wet. A suit that feels snug dry will typically feel better fitting in the water.
One important caveat: if a suit feels uncomfortably tight dry, it will still feel tight wet — the stretch doesn't add that much room. Proper fit starts dry.
Trying Before You Buy (In-Store Tips)
If shopping in person:
- Wear nude or seamless underwear under swimwear when trying on
- Move through the range of motions you'd use in the water — arms overhead, bending forward, squatting
- Check the crotch seam for comfort in multiple positions
- Look at the back — straps, coverage, and fit should look clean without pulling
Frequently Asked Questions
What if I'm between sizes?
For one-piece swimsuits and rashguards, size up. Swimwear that's slightly too large is more comfortable and functional in the water than swimwear that's slightly too small. For bikini tops specifically, some women buy separates in different sizes — a top in one size and a bottom in another — to match their proportions.
Should swimwear feel tight when I first try it on?
Snug, yes. Uncomfortably tight, no. Swimwear should have a secure, close fit that stays in place in the water — but you should be able to breathe fully, move freely, and not feel skin compression. If you feel any restriction in breathing or movement, try a size up.
How do I know if a rashguard will stay in place while surfing or swimming?
Raise both arms overhead and check that the hem of the rashguard doesn't ride up past your lower back. Then do a forward bend — the rashguard should stay in contact with your torso, not gap away from it. A rashguard that rides up during paddling will expose your lower back to sun and abrasion exactly when you need it least.
Do swimsuit sizes correspond to dress sizes?
Roughly, but not reliably. Swimwear sizing is independent of dress sizing in most brands. Always use your measurements against the specific brand's chart — don't assume your dress size translates directly. Many women find their swimwear size differs from their dress size due to different construction and stretch requirements.
How does Sailbee's sizing compare to other brands?
Sailbee sizes are designed for Southeast Asian body proportions — generally a better fit for the region's typical measurements than European or US brands. Check the size chart on each product page and compare against your bust, waist, and hip measurements for the most accurate result. If you have questions about a specific product's fit, feel free to contact us directly.
Shop SAILBEE for Asian-fit swimwear
Built for narrower shoulders, shorter torsos, and SEA water days. UPF 50+ on every rashguard, ships from our China warehouse to Southeast Asia in 3–7 days.
- Women's swimwear & rashguards — UPF 50+, Asian-fit cut
- Men's rashguards — Surf-ready, fits true
- Beach robes — Quick-dry, packable cover-ups
- Bestsellers — Our most-loved pieces from 1,237+ verified reviews
Not sure on size? See our Size Guide or email jun@sailbee.cn — we'll recommend a fit.