July 20th 2023

At Frog Bikes, sizing a child is taken very seriously! For cycling success and enjoyment, this is a crucial factor. NHS Staff Benefits members can receive a 15% discount when shopping with Frog Bikes!

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Frog Bikes

How to Measure Bike Sizes for Kids

Children’s bikes were historically sized using the wheel size rather than the frame size (the convention for adult bikes). On bikes that have the same size wheels and claim to be the same size, stand over height and saddle height are different due to the different frames of every manufacturer. Most people recommend choosing a child's bike based on their child's wheel size and age, but this isn't accurate. You need your child's inseam measurement! 

● AGE = No


● WHEEL SIZE = Worth considering


How age doesn't determine bike size 

Children are unique and come in all shapes and sizes, growing at different times. You can have extremes of height in all age categories so trying to fit everyone neatly into an ‘age 4’ box simply doesn’t work! 

How height doesn’t determine bike size 

Height is more useful than age but still not perfect. After all, between boys and girls, there may be a difference between leg length and torso length. Most girls tend to have longer legs and shorter torsos compared to their male counterparts, this will mean they may need a higher saddle position and maybe even a bigger bike than a boy of the same height. 

Why wheel size is worth considering 

Whilst many bike manufacturers use a similar wheel diameter on their frame sizes, some manufacturers have chosen to put larger wheels on smaller frames to increase stability. For this reason alone, using kids' bike wheel sizes to choose a bike isn’t always possible. Wheel size can be considered at a later stage once you have the inseam measurements. 

Why the inseam measurement determines the perfect fit 

The inside leg measurement is the most important! It is the best way to find the right bike size for kids. This way you can find out if when they are sat on the bike, they will be able to put their feet on the floor (when the saddle is at its lowest). In addition to this, you will be able to get an idea of how long the bike will be the right size for them - looking at the maximum saddle height.

How to measure a child’s inseam:

1. Stand your child in their socks (no shoes) against a wall 

2. Place a small book between their legs (with the spine upwards), as high as is comfortable! 

3. Ask the child to move away and measure from the spine of the book to the floor, this is your child’s inseam measurement

Bikes for young children

It’s that simple! Once you have your child’s inseam measurement, you can then consider what wheel size they will probably need. Generally speaking, younger kids who are only just learning to ride should have a balance bike with 10”, 12” or 14” wheels. This type of bike will teach children the necessary skills to balance, before advancing to pedals. If children are learning to ride at an older age, the pedals on Frog's first pedal bikes can also be removed to act as balance bikes for older/taller children. 

Bikes for older children

Often when kids get to the point, they need 26” wheels, they are forced into the adult category, where bikes weigh twice as much and will be a lot harder to handle. Frog offer Hybrid, Road, Track, MTB and City bikes in a 26” wheel size to ensure that a taller child isn’t penalised and forced to ride an adult bike before they’re ready.

Find your child’s fit 

The Frog Fit size guide offers size suggestions for confident and tentative riders alongside their inseam measurement. This is based on the idea that a confident rider won’t mind if just their tiptoes are on the floor when sat on the saddle, compared to a more cautious rider, who will want to feel their feet flat on the ground when seated on the bike. Click here to visit the Frog Fit guide.

What else should be considered?

Stand over height. The stand over height is the distance from the ground to the top tube of the bike frame. Frog Bikes recommends that your child can stand comfortably over the top tube of their bike (when they are standing with one leg on either side of the bike). Ensure your child’s inseam is at least as tall as the stand over height measurement. It’s best to have a little bit of extra room here too.

Minimum seat post/saddle height. Frog Bikes have long seat posts (and you can purchase an additional handlebar riser ) to ensure the bike can grow with your child and remain a good fit for as long as possible. It is also helpful to know the minimum seat post height to ensure your child can touch the floor. 

The minimum saddle height should be looked at in different ways depending on the bike: 

For a balance bike, the minimum saddle height should be no higher than your child’s inseam measurement. Ideally, the seat should be set at anywhere from 2 - 4 cm below your child’s inseam measurement. For example, if they have a 32 cm inseam you should set the saddle height around 28-30 cm (distance from the floor to the top of the saddle). Your child needs to be able to get his or her feet firmly on the ground to scoot and balance, if the saddle is too high then they will not be able to reach the floor to propel themselves forwards. This set-up also allows your child to place their feet flat on the ground with a slightly bent knee. The bend in their knee will allow them to run on the bike as they become more confident. 

For a first pedal bike, you should again be looking at a bike that has a minimum saddle height the same as your child’s inseam measurement. They should be able to touch the ground when seated on the bike allowing them to stop and start without toppling off. If they started with a balance bike and are already very confident this measurement can be 2-3cm higher than their inseam. This simply means they will be on their tiptoes rather than flat feet. As they become more confident the saddle can be raised a little higher allowing for better leg extension when pedalling, which will increase their pedalling efficiency. 

For their second pedal bike, it is fine to only be able to touch the ground with their tiptoes. A confident pedaller may even have the saddle position 5-10 cm higher than their inseam measurement. 

Why choose a Frog bike? 

Frog bikes are designed specifically for children. Along with the ethos to build bikes with the child at the centre of everything (from the components to the colours), Frog Bikes’ frame geometry has been specifically designed to give a child a comfortable and in-control riding experience.

Don't forget NHS Staff Benefits members are being offered an exclusive 15% discount from Frog Bikes - get all the details on how to redeem here.

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