How to Measure Your Child for Swimwear
Age labels are a rough guide at best. A tall nine-year-old and a small eleven-year-old can wear the same suit, and two brands can label the same size differently. Five minutes with a tape measure saves a lot of guessing. This guide sits within our kids swimwear guide for parents.
How do you measure a child for swimwear?
Use a soft tape measure, and measure over light underwear or close-fitting clothes. Ask your child to stand straight and relaxed, arms by their sides, breathing normally. Keep the tape level and snug, not tight.
Where to Measure
| Measurement | How to take it | Used for |
|---|---|---|
| Chest | Around the fullest part of the chest, under the arms | Girls swimsuits and kneesuits |
| Waist | Around the natural waist, usually just above the belly button | Boys jammers and trunks |
| Hips | Around the widest part of the hips and bottom | Kneesuits, jammers, swimsuits |
| Torso | From the top of one shoulder, down between the legs and back up to the same shoulder | One-piece suits for tall or long-bodied children |
How do you read a brand size chart?
Find the size where your child's measurements fall. If they're between sizes, check which measurement matters most for that suit: chest for girls swimsuits, waist for boys jammers. For one-piece suits, a long torso may mean going up a size even if the chest fits. Every brand is different, so check the chart for the specific suit you're buying.
The mistake: Buying the same size in a new brand because "that's what she wears".
What happens: Sizes vary between brands, so the new suit is too tight or too baggy. Your child won't want to wear it.
How to avoid it: Re-measure and check the chart for each brand. Our girls swimwear lists sizes on every product.
How should children's swimwear fit?
- Snug but comfortable when dry, as it relaxes slightly when wet.
- No gaping at the back or under the arms.
- Straps that stay on the shoulders without digging in.
- Leg openings that lie flat without cutting in.
Ask your child to crouch and stretch their arms overhead. If the suit pulls down at the shoulders, the torso is too short; if it gapes or bags, it's too big.
THREE MEASURING TIPS
THREE MEASURING TIPSRelaxed stance
Relaxed stanceStanding straight, arms down, breathing normally.
Snug tape
Snug tapeLevel and close, but not pulling tight.
Re-measure often
Re-measure oftenEvery few months during growth spurts.
What about boys swimwear?
Boys jammers and trunks are usually sized by waist, sometimes with an age band alongside. Measure the natural waist and check the chart. Our boys swimwear includes waist-size filters to make this easier.
How often should you re-measure?
Every few months, and before buying any new suit. Signs your child has outgrown a suit include straps digging in, the suit pulling down at the front and constant tugging. Avoid buying a size up to grow into; a baggy suit slips and lets water in. For half-term crash courses, our children's swimming kit guide covers what to pack. If your child is starting club training, read our guide to your child's first swimming club. For general sizing across adult and child ranges, see our swimwear guide. Our swimwear experts are always happy to check sizes over the phone.
Why Buy Kids Swimwear From Allens Swimwear
We've been sizing young swimmers for 50 years.
Written by a swimwear specialist at Allens Swimwear, 50 years of expert fitting. Updated 15 October 2026.
Frequently Asked Questions
How do I measure my child for a swimsuit?
Measure their chest, waist and hips with a soft tape, plus torso length for one-piece suits. Compare the numbers with the brand's size chart.
Should I buy children's swimwear by age?
Use age as a rough guide only. Measurements are far more reliable, because children of the same age vary a lot and brands size differently.
What if my child is between sizes?
Check which measurement matters most for that suit. For one-piece suits, a long torso often means the larger size; for training suits, the smaller size often fits better once wet.
How tight should a child's swimsuit be?
Snug but comfortable when dry, with no gaping at the back. It shouldn't dig in or restrict movement.
How often should I re-measure my child?
Every few months, and always before buying a new suit, especially during growth spurts.