How to Choose a Baby or Toddler Swimsuit: Fit & Sizing Guide

October 5, 2026

The best baby or toddler swimsuit fits snugly without squeezing, is easy to get on and off, suits the kind of swimming you're doing, and is paired with sun protection. This guide walks Australian parents through sizing, fit, swim nappies, sun safety and style, so you can choose with confidence.

1. Start with the right size, not just the age on the label

Baby and toddler sizes vary between brands, so use the size chart on each product page instead of guessing by age. Measure your child's chest, waist and height, then compare. Babies grow fast, so if your little one is between sizes, sizing up is usually the safer choice for comfort. Common sizes you'll see include 6-12 months, 18 months, 2T, 3T and 4T.

2. Check the fit: snug, not tight

Leg and arm openings: snug enough to stay in place in the water, with no red marks after wearing.
Straps: thin or wide straps should sit flat on the shoulders and not slip off when your child splashes or crawls.
Length: a one-piece should reach comfortably without pulling on the shoulders when your child sits or squats.

3. Pick the right style for your child

One-piece swimsuit: the classic choice for baby girls and toddler girls. Simple, secure and easy to match with a swim cap or hat.
Tutu or frill swimsuit: a one-piece with a tulle or rosette skirt, made for beach photos, holidays and parties.
Long-sleeve swimsuit or rash vest: extra coverage for longer days in strong Australian sun.
Swim shorts or trunks: a popular pick for baby boys and toddler boys.

4. Swim nappies: what to know before you buy

Many pools expect babies and toddlers who aren't toilet trained to wear a swim nappy. Some swimsuits have a built-in nappy layer, while others need a separate reusable swim nappy worn underneath. Check the product description so you know which you're buying, and ask the pool about its rules before your first visit.

5. Plan your sun protection

Swimwear is only one part of sun safety. Look for fabric labelled with a UPF rating if your child will be in the sun for long periods, and always follow Cancer Council Australia's advice: slip on clothing, slop on sunscreen, slap on a hat, seek shade and slide on sunglasses. A pretty tutu swimsuit is perfect for short beach moments, and a long-sleeve rash vest and wide-brim hat are a smart addition for all-day outings.

6. Add a swim cap for hair and style

A swim cap or bonnet keeps hair out of little faces and completes the look. Our guide to swim caps vs swim bonnets explains how to choose one.

Quick checklist before you buy

Measure your child and check the size chart.
Choose snug leg and arm openings with secure straps.
Decide whether you need a built-in or separate swim nappy.
Pick a style that suits the day: pretty for photos, coverage for long sun exposure.
Add a swim cap or hat, and plan for shade and sunscreen.

Frequently asked questions

What size swimsuit does a 1-year-old or 18-month-old need?

It depends on the brand, so always compare your child's chest, waist and height with the size chart. Many brands label this stage as 12-18 months or 18-24 months.

Does my baby need a swimsuit with a built-in nappy?

If your baby isn't toilet trained, they will usually need a swim nappy at the pool. This can be built into the swimsuit or worn separately, so check the product details.

Is a tutu swimsuit practical for toddlers?

Yes. A tutu swimsuit is a one-piece with a decorative skirt, so it works for paddling, beach play and holiday photos. For long days in strong sun, add a rash vest and hat.