In contrast to many kids' bikes, Frog bikes are sized by the leg length rather than age, as this is the most reliable way of getting the right size of bike for each child. Age alone isn’t a reliable measure as there is a large spread of “normal” leg lengths & heights for each age.

Please take the time to measure the rider’s inside leg. 
It’s easy to measure:

1. Stand the child in socks against a wall
2. Place a small book between their legs, as high as is comfortable
3. Ask the child to move away and measure from the top of the book to the floor, in inches.

Once you have measured the inside leg, use this table to find the right size of bike for your child. Note we give the MINIMUM inside leg length for each bike, with the saddle at its lowest setting. At this height, the child will safely and comfortably be able to get their feet on the ground. Don’t worry - Frog Bikes have long seat posts, so the saddle can be raised a long way as the rider grows.
We recommend that you go to a local store who will have many of our bikes available so the rider can sit on a bike. You will get help and advice on sizing, and get on-going service, as well as support.  
PLEASE NOTE we always recommend that you buy your Frog bike from your local stockist, who will build it for you and ensure the fit is right for your child.  Our bikes should always be built and checked by a qualified mechanic.
 

Of course all children have different length arms and torsos too, so to ensure a comfortable riding position, the handlebar height can be tailored, and saddles can be slid backwards and forwards on their rails. (These adjustments are easy to do and just need an allen key; instructions are in the manual).