Key points at a glance
- Your clothing or lingerie size does not translate reliably to swimwear.
- Tops and bottoms often fit differently and should be assessed separately.
- With a fuller bust, the cup size matters more than the dress size.
- Trying things on while moving tells you more than any size chart.
Why your usual size often fails
Swimwear has to do more than a summer dress. It sits close to the body, has to hold in the water, must not slip while swimming and still needs to support when wet. The fabrics are highly elastic, and wet fabric gives a little more. What feels snug when dry can become loose in the water.
On top of that, brands and cuts differ. A size 40 from one manufacturer is not necessarily a 40 from the next. Underwired bikinis or moulded cups follow their own logic, based on bra sizes but not always identical. With one-piece swimsuits, torso length also matters: if you have a long upper body, you will quickly feel the straps pulling even when the size is right.
With swimwear, fit is the real issue, not the number on the label.
Measuring and trying on properly
Before ordering or visiting a shop, a tape measure is worth using. Measure without clothes or in an unpadded bra:
- Underbust: snug, directly below the bust.
- Bust: loosely, at the fullest point.
- Hips: at the widest part of the seat.
- For swimsuits, torso length: from the shoulder through the crotch back up to the shoulder.
- Compare the figures with the specific brand’s chart, not with a generic one.
A glance in the mirror is not enough when trying on. Raise your arms, bend forward, sit down and turn around. Only then will you see whether the cup supports the bust, the straps dig in or the bottoms slip.
Practical tip
Try tops and bottoms separately in different sizes. Many retailers sell the pieces individually, so you can combine, for example, a larger top with a smaller bottom.
Spotting fit problems
Most problems can be read from a few signs. The table helps you interpret them.
| Symptom | Possible cause | What helps |
|---|---|---|
| Bust spills over the cup | Cup too small | Choose a larger cup with the same band |
| Cup gapes or wrinkles | Cup too large or wrong shape | Try a smaller cup or a different cut |
| Straps dig in | Too little support from the band | Firmer band; avoid halter necks |
| Bottoms slip or wrinkle | Too large, especially once wet | Test one size smaller |
| Swimsuit pulls at shoulders and crotch | Torso cut too short | Look for a longer-torso model |
Online or specialist shop?
Online you see colour, cut and size, but not how a model behaves on your own body. If you know your size in a particular brand, reordering online works well. For a first purchase, a fuller bust or after physical changes such as pregnancy or weight loss, a fitting with advice is usually more efficient.
Specialist shops often carry a wider size range than department stores; according to the retailer, Perosa for example stocks sizes 34 to 52 with cups from A to H. More choice does not make the decision simpler, but more precise: there are more combinations, and advice helps narrow them down.
When buying online, also factor in the hidden costs of a wrong purchase: returns, waiting time and reordering. For hygiene reasons, bottoms can often only be exchanged with the protective liner intact. Check the return conditions before you buy.
With foreign shops, also check the size system. British, American, French and Italian sizes differ from the German sizes commonly used in Switzerland, and cup letters beyond D are labelled differently from country to country. A conversion chart helps, but it does not replace trying things on.
Frequently asked questions
Is there a simple rule for the right bikini size?
Should swimwear fit tight or loose?
Is my bra size the same as my bikini size?
Is a specialist shop automatically more expensive?
When should I buy swimwear?
Accepting that fit matters more than your usual size is the surest way to make better choices and avoid wrong purchases.