Sizes for a 3 year old

Clothes, shoes, bike, scooter, helmet and bedtime sizes for a 3 year old, all on one page and taken from UK retailers' own charts.

Checked against UK retailer charts on 18 October 2026.

Clothes

Usually 3–4 years (cut for up to 104 cm at Boden)

Shoes

Typically around UK 7 to 8.5, but measure their feet

Bike

Balance bike or 12" / 14" wheels

Bike helmet

Kids size, about 48–54 cm head circumference

Duvet

4.5–9 tog depending on season

School uniform

Chest about 24", waist about 20"

Clothes

UK shops label children's clothes by age but cut them to a height. A label like "3–4 years" fits a child from their 3rd birthday up to their 4th, so a 3 year old is usually in 3–4 years. Boden prints the maximum height for each label:

John Lewis uses single-age labels. Its "3 years" size is cut for the height a child reaches at 3, which is the same as Boden's "2–3". That is why one shop's 3 feels small next to another's 3–4.

If they're between sizes, go by height first, then chest for tops and waist for bottoms. More on this in kids’ clothes sizes by height.

Shoes

Two UK shoe shops publish an "average size by age". They don't quite agree, so you get a range:

Feet vary more than height does, so measure heel to longest toe in centimetres and use the kids’ shoe size chart by foot length. Buying a European brand? Use the EU to UK shoe size converter.

Bike

A balance bike is still the usual choice at 3. A 12" fits most 3 year olds; a 14" (Hornit: inside leg 40–53 cm, 3.5+ years) lasts longer for taller children. If they want pedals, Trek lists 12" for 2–4 years.

Cycling UK's rule of thumb: the wheel diameter in inches should be no bigger than the child's inside leg in inches. Full tables in the kids’ bike size chart and the balance bike size guide.

Scooter

A three-wheel "mini" scooter. Micro designs its Mini for ages 2–5. Whatever the brand, the handlebar should sit somewhere between belly button and mid-chest. See scooter size by age.

Bike helmet

Halfords' guide puts 3 year olds in its Kids size (3+ years), 48–54 cm. Helmets are sized by head circumference, not age, so measure about two finger-widths above the eyebrows. Fit checks are in the helmet size guide.

Bed and duvet

Dunelm suggests 4.5–9 tog for children over three, depending on the season: about 7.5 tog in winter and 2.5–4 tog in summer. A single bed takes a 135 × 200 cm duvet.

More detail in what tog duvet for a child and what to wear to bed by room temperature. Pyjamas follow the same age labels as clothes: see kids’ pyjama sizes.

School uniform

Uniform is often sold in inches. Your School Uniform's chart puts the 3/4 yrs age band at:

Full chart and how to measure: school uniform sizes explained.