Frog Bike Size Guide: Which Frog Bike Is Right for Your Child?

Frog bikes are some of the lightest, best-loved kids' bikes around, but sizing them isn't quite as simple as "my child is five, so I'll get the age 5 bike." Frog does things differently, and it's worth knowing why before you buy.

Forget age. Measure the inside leg.

Frog size their bikes by inside leg length, not age or height. Two five-year-olds can have completely different leg lengths, so age is a rough guess at best, inseam is the number that actually tells you whether your child can get their feet safely on the ground.

Here's how to measure it in thirty seconds:

That number is your starting point. Head here for our complete guide on how to measure you child for a bike. 

The Frog range at a glance 

A few things worth knowing:

• These are minimum leg lengths, measured with the saddle at its lowest. Frog's long seat posts mean there's plenty of room to grow before you need the next size.

• If your child sits between two sizes, size up only if they're already a confident rider, a bike that's a stretch too far can knock a nervous rider's confidence.

• Balance bikes (10"–14" wheels) come before all of this, for children just learning to balance before they pedal.

Why this matters more than it seems

Get the size wrong and it shows fast: knees hitting handlebars, tiptoes barely reaching the ground, a wobbly ride that puts a child off cycling before they've properly started. Get it right, and the improvement in confidence is immediate a lighter, better-fitted bike makes learning easier, not just more comfortable.

The easy way to always have the right size

Kids don't measure their own growth spurts, they just quietly stop fitting the bike you bought them eight months ago. That's exactly why Bike Club exists: our fleet includes Frog bikes across every size, and when your child's inside leg outgrows theirs, you simply exchange it for the next one up. No re-measuring, re-selling, or guessing twice.