How to easily measure your child for a new bike

Measuring your child before you buy them a new bike is really important to help make sure you’re buying a bike that will fit them and they’ll love riding.  A properly sized kids bike is crucial to the safety and enjoyment of cycling – buy one that’s too big and they’ll be nervous and won’t want to ride it.  Buy too small and they’ll grow out of it in no time! 

Measuring your child accurately and buying a bike that they’re at the lower end of the range will ensure they get maximum use out of it and can start riding it immediately. 

How to easily measure your child for a new bike

Most quality kids bikes will provide you with an inside leg measurement range, and others will also give you height guidelines, so these are the two measurements you need to know before you start shopping for a new bike for your child. 

What you’ll need:

  • A lucky new bike recipient
  • A wall you’re happy to make three small pencil marks on
  • A straight edge (spine of a hard backed book or a cereal box is best)
  • Tape measure
  • Pencil
  • Paper or phone to note measurements

How to measure your child’s inside leg for a new bike:

Inside leg is a crucial measurement to ensure the bicycle you’re buying is the correct size.  

Most quality kids bike manufacturers will give you an inside leg measurement range, others will just supply a minimum measurement. 

Note on American bikes this may be called the inseam. 

It is VERY important that you don’t buy a bike that is too big as they won’t be able to ride it. Aim for a bike where your child’s measurement is towards the lower end of the manufacturers stated range, to give plenty of room for growth, but do not go below it, or the bike will be too big. 

For example, if your child’s inside leg is 49cm don’t be tempted to buy a bike that says a minimum inside leg of 52cm as they will struggle to get their feet onto the ground. You’re better off getting one with a minimum inside leg of 48cm (or slightly lower) as the seat post on a quality kids bike can be raised to allow plenty of room for growth. 

Note – inside leg measurement means you are measuring the distance from the floor to their groin – not the width around their leg! 

  1. Stand the child with their back against the wall in socks (no shoes).
  2. Place the straight edge of a hardbacked book between their legs and slide it up the wall until it meets their crotch firmly. Make sure you remember which way up the book is as you may need to know this later. 
    It’s important at this point to make sure the edge is sitting against their crotch and that you’re not getting a false measurement from the material of their clothing. 

  3. Make sure they don’t try and go onto tip toes at this point – many kids want to appear taller! 
  4. You can try and make a mark against the wall where the top end of the book is against your child’s crotch, but we find this can be quite difficult –  especially with wriggly or ticklish children.  Instead, mark where the bottom edge of the book meets the wall (make sure you ask the wall owners permission!).
  5. Move the book and allow your child to move away from the wall. 
  6. Replace the base of the book against your measurement, making sure it’s the same way up and completely straight. 
  7. Mark the top of the book – this is your child’s inside leg measurement.  You can double check by bringing your child back to stand next to the marks and repeat steps 2 and 3 to visually check you’ve got this correct. 
  8. Measure from the ground up to the TOP mark on the wall – this is your child’s inside leg measurement.  

NOTE:  The two places where it’s easy to go wrong are measuring to the bottom mark or turning your book in a different direction. 

How to measure your child’s height for a new bike:

Many bike manufacturers will give a height range for their bikes – this takes into account leg and body position on their bikes.  

  1. Stand the child with their back against the wall in socks (no shoes).
  2. Make sure they are stood up straight, no going on tiptoes or bending the knees.
  3. Place the straight edge across the top of the head, parallel to the floor.  You can use a book, like this:

    How to measure your child's height for a new bikeCYCLE SPROG TOP TIP:  If you’re worried your book isn’t level, then use a very thick hardbacked book or a cereal box instead.  The side of the box against the wall will ensure that it’s at 90º meaning you measure to the correct point.

  4. Mark your child’s height on the wall, making sure to mark where the bottom edge of the book/box contacting the wall. 
  5. Measure from the ground up to mark on the wall, make a note of it.

Note:  The two places where it’s easy to go wrong are having the book dipping down rather than perpendicular to the wall, and measuring to the top of the book, rather than where it meets your child’s head. 

You’re now equipped with the two piece of information to allow you to go and choose the perfect bike for them.   Why not check out our article The Best Kids Bikes to get started in your search? 

Take a moment to GRAB YOUR FREE KIDS BIKE BUYING CHECKLIST which will help you record all the information you need to find the perfect bike for your child. 

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