Swimsuits · Guide
Bathing Suit Sizes
Four measurements, two sizing systems, and one rule: never buy to your dress size.
The short answer
Bathing suit sizes do not match clothing sizes. Measure bust or chest, waist, hips and torso length, then buy against that brand's own chart. Women's swim runs in both alpha (S-XL) and numeric (6-20) sizing; men's trunks run by waist in inches. Swimwear is cut snug, so between sizes, size up only for a one-piece.
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Swim sizes are not clothing sizes
This is the whole problem in one line. A bathing suit is cut to be held under tension against a body, so the garment is deliberately smaller than the body it fits. Clothing is cut with ease. Buying swimwear to your dress size produces a suit that is somewhere between slightly loose and badly wrong, depending on the brand.
On top of that, swimwear brands do not share a chart. A size 12 in one brand is a different set of inches from a size 12 in another, and alpha sizing — S, M, L — is even looser as a standard. There is no shortcut around this: you measure, and then you read that brand's numbers.
The good news is that the measuring takes three minutes and only has to happen once a year, and nearly every brand worth buying publishes a real chart in inches.
The four measurements
- Bust or chest — around the fullest part, tape level and snug but not pulled tight. For women, wear a non-padded bra or none at all.
- Waist — around the narrowest part, usually about an inch above the navel. Do not hold your breath in.
- Hips — around the fullest part of the seat, feet together.
- Torso length — from the top of one shoulder, down the front, between the legs, and back up to the same shoulder. This is the measurement almost nobody takes and the one that explains most one-piece complaints.
Write them down. Then, for every suit you consider, compare all four against that brand's chart rather than picking the size you usually wear. If the brand publishes only bust and waist, the torso measurement still tells you whether to look for a long-torso option.
Lands' End Chlorine Resistant Tugless Tank
The one major brand that treats long torso, D-cup, DD-cup and plus as cataloged fits rather than as exceptions.
Specifications
- Fabric
- 77% nylon / 23% LYCRA Xtra Life
- UPF
- 50
- Support
- Soft cup bra, no underwire
- Fits
- Regular, long torso, D/DD cup, plus
What works
- Long torso and cup-sized versions are separate fits, not a larger copy of the same pattern — the actual fix for a suit that digs at the shoulders
- LYCRA Xtra Life is the chlorine-resistant grade of spandex; Lands' End states it lasts up to ten times longer than standard spandex
- The soft cup shelf bra supports without an underwire that eventually rusts and digs
- UPF 50 across the body, which matters if you spend the afternoon standing in open water
What doesn’t
- Nylon and spandex, so chlorine-resistant rather than chlorine-proof — a daily lap swimmer will still wear it out faster than a polyester-PBT suit
- List price is high and the brand discounts so often that buying at full price feels like bad timing
- Sporty and modest by design; nobody buys this suit for the styling
Who it’s for
A parent in and out of the water all day who has never found a suit that fits a long torso or a fuller bust.
Bottom line
The fit brand. Buy it on one of its frequent sales rather than at list, and buy the specific fit rather than sizing up.
Speedo Women's Endurance+ Super Pro
Endurance+ fabric is the genuine article — it outlasts standard swim fabric several times over in chlorine.
Specifications
- Fabric
- Endurance+ (PBT), 100% chlorine-resistant
- Back
- Super Pro, high coverage
- Sizes
- Women's 28-40
- Lining
- Fully lined
What works
- PBT fabric does not degrade in chlorine — the fabric, not a coating, is what makes this last
- Super Pro back holds the shoulders without cutting in over a long swim
- Holds compression across a full season rather than going slack
- Fully lined, so it stays opaque wet
What doesn’t
- PBT has less stretch than standard swim fabric and feels firmer
- Costs roughly double a fashion one-piece
Who it’s for
A woman swimming laps weekly, or anyone tired of replacing a suit every summer.
Bottom line
Cheaper per swim than any fashion suit. If you swim in chlorine regularly, this is the only sensible fabric.
Speedo Men's Marina Volley Trunk
A short quick-dry volley trunk built to swim in, with a liner and a pocket that drains.
Specifications
- Length
- Approx. 8 in inseam
- Waist
- Elastic with drawcord
- Liner
- Mesh
- Back, drainable
What works
- Short enough to actually swim in — long board shorts fill with water and drag
- Quick-dry fabric means you are not sitting in a wet trunk for an hour after
- Drainable pocket does not hold a liter of lake water
- Priced to own two
What doesn’t
- Above-knee length is not to everyone's taste
- Liner will irritate some wearers
Who it’s for
Anyone who swims rather than wades — laps, lake crossings, keeping up with children.
Bottom line
Buy by inseam, not by brand. Anything past the knee is a beach garment, not swimwear.
Kanu Surf Men's Swim Trunks
Basic quick-dry trunks at the bottom of the price range, with a drawcord and pockets that work.
Specifications
- Length
- Various, mid to knee
- Waist
- Elastic with drawcord
- Liner
- Mesh on most models
- Fabric
- Quick-dry polyester
What works
- Cheapest trunk here that still has a working drawcord and a mesh liner
- Wide size range including big and tall
- Dries acceptably fast
- Cheap enough to buy three and stop thinking about it
What doesn’t
- Fabric is thinner and fades over a season
- Fit consistency varies between models
Who it’s for
Anyone needing trunks for occasional use, or several pairs for a family holiday.
Bottom line
The budget pick and honestly fine. The Speedo lasts longer and swims better if you are actually swimming.
Women's sizing: three systems in one category
| System | Looks like | Used by | Sized from |
|---|---|---|---|
| Alpha | XS, S, M, L, XL | Fashion and resort swim | Bust and waist, loosely |
| Numeric (US) | 4, 6, 8 … 20 | Most department-store swim | Bust, waist and hip in inches |
| Team / training | 26, 28, 30 … 40 | Speedo, TYR, Arena, Dolfin | Chest in inches |
| Cup sizing | 34C, 36DD | Suits with built-in bras | Band plus cup |
Training sizes are the clearest of the four, because the number is just a chest measurement in inches. If you have ever wondered why a Speedo "32" fits nothing like a dress size 32, that is why — they are measuring different things, and the training number is the honest one.
If you need real bust support, look for a suit sold in band-and-cup sizes or one with a soft-cup shelf bra and a published D/DD range. A one-piece with a shelf bra in alpha sizing provides shape, not support, and no amount of sizing down converts one into the other.
Men's sizing: simpler, with one trap
Men's swim trunks are sold by waist in inches or in alpha sizes mapped to a waist range, and the elastic waistband with a drawcord forgives a lot. Buy your usual trouser waist and it will usually be right.
The trap is inseam, not waist. Trunk length ranges from about a 5-inch inseam to past the knee, and the length changes what the garment is for: a short inseam swims, a long one is a board short that wades. Check the stated inseam rather than the photo, because the model's height does the work in the photo.
The other thing to check is the liner. A mesh liner is standard and it is what makes a trunk swimmable; a brief liner is warmer and slower to dry. The picks by use are in best men's swim trunks.
What to do when you are between sizes
- One-piece, between sizes: size up, and check the long-torso option. A one-piece that is too short pulls down at the shoulders and rides up, and no adjustment fixes it.
- Two-piece, between sizes: buy the top and bottom separately if the brand allows it. This is the single best feature of separates and most people never use it.
- Training suit, between sizes: size down. These are meant to be tight and they relax in water.
- Men's trunks, between sizes: size down if the drawcord is good, up if the waistband is wide and soft.
- Children, between sizes: buy the current size. A loose swimsuit on a child drags, rides up and gets refused — see kids' swimsuit size chart.
Why the suit still does not fit
If the measurements were right and the fit is wrong, the cause is almost always one of three things: the torso length, the leg cut, or the bust style. A suit can match your bust, waist and hip perfectly and still be wrong because it is cut for a shorter body, a higher leg, or a different bust shape.
That is a pattern problem rather than a size problem, and the fix is a different cut from the same brand or a brand that publishes more fit options. The specific symptoms — gaping at the chest, digging at the leg, riding up at the back — are diagnosed one by one in swimsuit fit problems.
Questions
Frequently asked questions
Do bathing suit sizes run small?
How do I know my bathing suit size?
What does a size 32 swimsuit mean?
Should I size up or down in a bathing suit?
How are men's swim trunks sized?
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