Updated August 2026
"What size bike for a 5-year-old?" is the wrong question. The height difference between five-year-olds is easily 20 centimetres, and that spans two size steps.
The right question is: what size bike for a child with a 44 centimetre inseam? That one has a precise answer.
The short answer
Kids' bike size is chosen by inseam measurement, not by age and not even by height. Roughly: 12" suits a 35–42 cm inseam, 14" 40–48 cm, 16" 44–55 cm, 20" 51–63 cm and 24" 60–73 cm. The most important check is that the child can reach the ground with both feet from the saddle. Don't buy a size up to grow into.
Why age is a poor measure
Age charts are the most common and the least accurate thing in a bike shop. Children of the same age vary widely in height, and even within a given height the relative length of the legs varies.
Inseam determines two things that define safety: whether the child can reach the ground from the saddle, and whether they can reach the pedals without the knee coming up too high. Neither follows from age.
How to measure your child's inseam
- The child stands without shoes, back against a wall, feet about 15 cm apart.
- Place a book between their legs horizontally and press it gently upward.
- Measure from the floor to the top edge of the book.
It takes a minute and is considerably more reliable than any age chart.
Size chart by inseam
| Wheel size | Inseam | Child's height | Age (indicative) |
|---|---|---|---|
| 12" | 35–42 cm | 85–100 cm | 2–4 yrs |
| 14" | 40–48 cm | 95–110 cm | 3–5 yrs |
| 16" | 44–55 cm | 105–120 cm | 4–6 yrs |
| 20" | 51–63 cm | 115–135 cm | 6–9 yrs |
| 24" | 60–73 cm | 130–145 cm | 8–12 yrs |
| 26" | over 70 cm | 140 cm + | 10 yrs + |
The ranges overlap deliberately. If the measurement falls between two sizes, choose the smaller one – reasons below.
Woom's numbering tells you the size directly
This makes choosing considerably easier. The model number on a Woom kids' bike corresponds directly to the size step, and the wheel size is in the model name:
| Model | Wheel size | Child's height |
|---|---|---|
| Woom GO 1 | 12" | 82–100 cm |
| Woom GO 2 | 14" | 95–110 cm |
| Woom GO 3 | 16" | 105–120 cm |
| Woom GO 4 / Explore 4 / OFF 4 | 20" | 115–130 cm |
| Woom Explore 5 / OFF 5 | 24" | 130–145 cm |
| Woom Explore 6 / OFF 6 | 26" | 140 cm + |
Once you know the size step, you choose the model family by intended use:
- GO – the lightest, for a first bike and everyday riding
- Explore – equipped for touring, with mudguards and lights
- OFF and OFF Air – for off-road use; OFF Air has a suspension fork
Note that a suspension fork adds weight. On a bike under 24 inches it's only justified if the child genuinely rides off-road.
Three checks in the shop
1. Feet to the ground. With the child sitting in the saddle, the balls of both feet should reach the ground. For a complete beginner, preferably the whole foot – it gives confidence.
2. Hands to the bars. They should reach the handlebar with elbows slightly bent, not stretched out straight.
3. Brake levers. The child should be able to squeeze the brake lever with one or two fingers without letting go of the bars. This is the check most often skipped and it matters for safety – on quality kids' bikes the levers can be adjusted closer to the bar.
Why growing room is a bad idea
A bike that's too big is always also too heavy relative to what the child can handle. They can't lift it after a fall, turn it in a tight space, or hold it upright when setting off.
The result isn't slower learning but giving up. The child decides cycling isn't for them, and the parent reads it as a personality trait.
Growing room is handled by raising the saddle and handlebar, not by skipping a size. A good kids' bike usually has enough adjustment for one to two growing seasons.
From balance bike to pedal bike
A balance bike teaches balance, which is the hard part of cycling. Once balance is secure, the move to a pedal bike usually happens in a single afternoon – and without stabilisers.
Stabilisers teach the opposite skill to the one cycling requires: they prevent leaning, which is the basis of cornering. If they are used, they should come off as soon as possible.
The transition typically happens between four and five years old, but what matters is the security of the balance, not the age.
Gears and brakes by size
Under 16": no gears. Single-speed is lighter and more durable, and the child doesn't benefit from gears yet.
16–20": gears are useful if there are hills on the route. One chainring and a few rear gears is plenty.
24" and up: gears are worthwhile, and disc brakes are a justified addition if the child rides off-road.
On brakes: a coaster brake alone isn't enough from 20 inches up. Hand brakes teach proper braking technique and work even if the chain comes off.
Weight is the single most important specification
Once the size is right, the next question is weight. A kids' bike shouldn't weigh more than 30% of the child's own body weight – a typical supermarket bike weighs more than half. We cover this in our kids' bike weight article.
Frequently asked questions
What size bike for a 3-year-old?
Usually 12 inches, with an inseam of 35–42 cm. Many three-year-olds are still on a balance bike.
What size bike for a 5-year-old?
Typically 16 inches, with an inseam of 44–55 cm and a height of 105–120 cm. Measure your child – five-year-olds vary a lot.
What size bike for a 7-year-old?
Typically 20 inches, with an inseam of 51–63 cm.
What size bike for a 10-year-old?
Typically 24 inches, with an inseam of 60–73 cm. A tall child may already move to 26 inches.
What do the Woom model numbers mean?
The model number corresponds to the size step and the wheel size is in the name: GO 1 is 12", GO 2 is 14", GO 3 is 16", the 4-series 20", the 5-series 24" and the 6-series 26".
Should the child reach the ground with the whole foot?
For a complete beginner, preferably yes, because it gives confidence. Once riding is secure, the balls of the feet are enough.
Does a child need stabilisers?
Usually not. Balance learned on a balance bike transfers directly to a pedal bike. Stabilisers prevent leaning, which is the basis of cornering.
Summary
Measure the inseam and forget the age charts. If the measurement falls between two sizes, choose the smaller – it's safer and the child learns faster on it.
Then check three things: feet to the ground, hands to the bars with elbows bent, and fingers to the brake levers without letting go.
We're happy to help with sizing – bring your child in to be measured at our Tampere store, or give us the measurement by phone: myynti@emiliasport.fi or +358 50 470 4686.
Browse our range: kids' and junior bikes.
Written by the Emilia Sport team
Emilia Sport has been a bike shop since 1978. We measure children for bike sizes at our Tampere store every day. We're happy to help by phone too: myynti@emiliasport.fi / +358 50 470 4686.
