What size bike does my child need?

Children's bikes are sold by wheel diameter — 12, 14, 16, 20, 24 and then 26in or adult sizes — and the charts that map wheel size to age are only a rough starting point, because children of the same age vary enormously. Fit is decided by the child's leg length against the bike's minimum saddle height, and by whether their hands can work the brakes.

Safety

What you'll need

• A tape measure
• The shoes they will ride in
• A wall and a book for the inside leg measurement

Step by step

1. Measure the inside leg properly.Shoes on, back to a wall, feet slightly apart. Put a hardback book between the legs, spine up, pulled up firmly as a saddle would be. Measure from the top of the book's spine to the floor. That figure is what everything else is checked against.
2. Find the bike's minimum saddle height, not its wheel size.Good manufacturers publish minimum and maximum saddle height for each model. The minimum must be at or below the child's inside leg measurement, or they cannot put their feet down. Two bikes with the same wheel size can differ by several centimetres here.
3. Set feet flat for a beginner.A child learning to pedal, or one who has just come off a balance bike, needs to be able to sit and put both feet flat on the ground. That is what makes stopping feel safe and it is why they will get on it a second time. It costs a small amount of pedalling efficiency and buys all the confidence.
4. Raise the saddle once they are confident.A confident rider wants a leg that is almost straight at the bottom of the pedal stroke, with the balls of both feet reaching the ground when seated. This is much more efficient and it is what stops a child complaining that pedalling is hard.
5. Check standover clearance.Standing over the top tube, flat-footed, there should be a clear gap between the child and the frame. If they are pressed against it, the bike is too big and getting off in a hurry will hurt.
6. Check they can reach and use the brakes.Sit them on the bike and have them squeeze each lever as hard as they can. Small hands need short-reach levers, and most children's levers have a reach adjustment screw. If they cannot lock the wheel, the bike is not safe for them regardless of how well it fits otherwise.
7. Weigh the bike.Many cheap children's bikes weigh nearly as much as the child. A bike that heavy is genuinely hard to control, hard to pick up and hard to enjoy. Weight is the specification worth paying for on a child's bike.
8. Skip stabilisers and start with a balance bike.Balance is the hard part of riding and stabilisers prevent it being learned — they teach a child to steer a tricycle and then take the tricycle away. A balance bike, or a pedal bike with the pedals removed and the saddle low, teaches balance first and the transition to pedals then takes minutes.
9. Buy used, and sell it on.Children outgrow bikes in two years while barely wearing them out. Good second-hand children's bikes hold their value, so the real cost of a decent lightweight bike is far lower than the sticker price.

Tips

• Take the child to the shop. Ten minutes of sitting on three bikes tells you more than any chart.
• Check the reach to the handlebars as well — a child stretched out over a long frame cannot steer accurately.
• Lower the saddle for the first few rides on any new bike, then raise it a centimetre at a time as confidence grows.
• Single-speed is fine, and often better, until they are riding proper distances. Gears are one more thing to go wrong and one more thing to think about.
• A bike with a coaster brake alone is a poor choice in the UK, where children learn hand brakes and the roads are hilly enough to need two of them.

Common mistakes

• Buying a size up so it lasts — The child cannot get a foot down, cannot control it, and will not ride it. You will end up buying the right size anyway, having lost a year of riding.
• Fitting stabilisers to teach riding — They teach the child to lean the wrong way and to rely on a support that must eventually be removed, which turns learning into a distinct and frightening event rather than a gradual one.
• Choosing a heavy full-suspension look-alike from a supermarket — The suspension does nothing, it adds several kilos to a bike a small child has to lift and control, and the brakes on those bikes are usually poor.

Questions people ask