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Find Your Size

What size bike does my child need?

Enter your child's inside leg and height. You get the wheel size, the rule and its source.

Nominal wheel sizes, inThe makers' bikes in our chart

Your child

Units for height and inside leg

Measure in socks, standing against a wall. How to measure inside leg

Your size

Your size appears here once both measurements are in.

Not measured yet? See how to measure.

Before you buy

  1. Measure the inside leg. Cycling UK says not to go by trouser size.

    Source: Cycling UK, the right size bike for a child (external site) checked

  2. Check the limits for the exact model. If you buy online and your child sits between two overlapping sizes, Cycling UK suggests asking the retailer.

    Source: Cycling UK, the right size bike for a child (external site) checked

  3. Arrange a test ride if you can, as woom advises. When your child stands over the bike with feet on the ground, woom says there should be a visible gap between the top of their legs and the top tube.

    Source: woom UK size page (external site) checked

Models we checked

No checked models in this size yet. The size above still stands.

More children's bikes on Amazon UK

How to measure inside leg and height

  1. Stand your child with their back to a wall, in socks, with feet flat on the floor.

  2. Place a book between their legs.

  3. Slide the book up the wall until it meets the crotch firmly.

  4. Mark the wall at that point.

  5. Measure from the mark straight down to the floor. That is the inside leg.

  6. For height, place the book flat on their head, mark where the bottom of the book touches the wall and measure straight down to the floor.

Source: Islabikes size chart (external site) checked

woom measures for its own chart with lighter pressure: the book goes up to the crotch with the same slight pressure that you'd get on the saddle while riding. The steps above press firmly, as Islabikes does, so before you choose a woom bike, measure again woom's way and enter that figure to check woom's rows.

Sources: woom inseam table (external site) checked ; Islabikes size chart (external site) checked

Your rows in the makers' charts

Once you enter the measurements, this shows only the rows of the makers' own charts that your child's measurements match, with each maker's model names and years as printed. A child fits a row when their inside leg and height are both inside it: Islabikes says the rider must meet both minimums. The full charts are on the makers' own sites, linked under How we worked it out.

Source: Islabikes size chart (external site) checked

How we worked it out

We read the Islabikes size chart and the woom inseam table row by row. A model fits when your child's inside leg and height are inside every limit its maker prints. Islabikes calls its minimums absolute: the rider must meet both the height and the inside leg minimum.

Wheel sizes come from the makers too: the Islabikes Cnoc spec sheet and the woom UK size page. Where a maker prints no wheel size for a model, we name the model and give no wheel size.

The charts include balance bikes: Islabikes' Rothan bikes and woom's GO 1 and GO 1 PLUS. We list them apart from the pedal bikes, and the wheel range in the answer comes from pedal bikes unless only a balance bike fits.

When a model fits, the answer is labelled Depends on the maker; when none does, it is labelled No recommendation. woom says height is the biggest factor, Cycling UK sizes the wheel from the inside leg, and on some brands a child will fit a bike with wheels the next size up, so the same child can fit different wheel sizes from different brands.

Beside the answer we show Cycling UK's rule of thumb: a wheel no bigger than the inside leg, both in inches. Its own example is a 41 cm (16 in) inside leg, which gives 16 in wheels at most.

Islabikes prints older models in the same rows as newer ones. We name each one with the years Islabikes gives, joining back-to-back years into one span, so check which generation a second-hand bike is. The wheel size from Islabikes' current spec sheet belongs to the current model only.

We do not ask for age. Cycling UK calls age a blunt indicator and says height and inside leg are much more reliable guides.

Every source on this page

Something wrong? See Corrections.

Questions

What size bike for a 5 year old?

Measure instead of going by age: Cycling UK calls age a blunt indicator. Islabikes prints rough minimum ages, for example 5 years for its Beinn 20, but its real limits are inside leg and height.

Sources: Cycling UK, the right size bike for a child (external site) checked ; Islabikes size chart (external site) checked

My child fits two sizes. Which one?

The sources differ. Cycling UK says to choose the biggest size your child can comfortably fit on. woom says not to size up for your child to grow into the bike.

Sources: Cycling UK, the right size bike for a child (external site) checked ; woom UK size page (external site) checked

woom says riding ability matters more than leg length: a child with well-developed motor skills will do fine on a slightly larger bike, while a less confident child of the same size would struggle on it. For a confident child who reaches the ground only on tiptoes on the next size up, woom says the smaller bike will be easier to handle.

Source: woom UK size page (external site) checked

If you can, Cycling UK suggests taking your child to the bike shop.

Source: Cycling UK, the right size bike for a child (external site) checked

What does "with the long seatpost" mean?

Some Islabikes rows print a second, larger inside leg limit for the bike with a long seatpost fitted. When your child is inside only that larger limit, we list the model with that note, so check that the bike you buy has the long seatpost.

Source: Islabikes size chart (external site) checked

What are the Cnoc dwarfism bikes?

They are Islabikes' Cnoc bikes for children with dwarfism, which Islabikes lists in a separate table of children's dwarfism bikes. We show them in their own table and never as the main answer.

Source: Islabikes size chart (external site) checked