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What Size Bike do I Need?

What Size Bike do I Need?


Having the wrong size bike can really ruin your experience on the road. If the top tube is too high, you may struggle to mount the bike and if the seat is too low, your knees may come up too high while you're riding. So, it's important that your bike is the right size for you in order to cycle safely and comfortably.

The bike frame size you need will depend on your height, cycling style, gender and the kind of bike you want to buy. In this buying guide, we will cover everything you need to do when buying a bike to ensure it is the right size, including:

  • Measuring your height
  • The type of bike
  • Choosing the right bike size
  • What size bike does my child need
  • FAQs

Measuring Your Height

If you don't already know how tall you are, stand against the wall and ask a friend or family member to measure. Stand up tall with your heels against the wall and measure from the highest point on your head, down to the ground. You may want to make a pencil mark on the wall of where your tallest point is so you can measure again to double-check you've recorded your height correctly.

Another key measurement you need is your inner leg. Again, stand up tall against the wall and make a mark on the wall at the top of your inner thigh. Or, hold a book between your legs and measure from the book to the ground to get your inner leg measurement.

Finally, you need to measure your arms. This is so you can get the right size frame to ensure your upper body is not too close or far away from the bike handles. So, to know whether or not you need a larger frame, you need to spread out your arms in a straight line and measure from fingertip to fingertip. Once you have the measurement, subtract your height. This will give you your ape index. If you get a negative number then you will need a small to medium frame, but if your Ape index is over 1, we suggest going for a larger frame.

The Type of Bike

The type of bike you are getting will determine the specific size bike you need. Mountain bikes and road bikes have completely different riding positions and are designed for completely different terrain. So, the type of bike you want will determine the frame size you need.

If you're not sure which bike is best for you, take a look at the different bike styles below.

Mountain Bike

Mountain bikes are designed for off-road cycling on uneven terrain and as a strong frame with thick tyres. The riding position on a mountain bike is more upright with a slight bend in the arms.

Road Bike

Road bikes are designed for cycling along pavements and roads at speed. The riding position involves leaning forwards towards the handlebars and maintaining a low, streamlined position.

Hybrid Bike

Hybrid bikes are designed for use as both a road bike or a mountain bike. They are most suited to general riding and commuting and tend to force the user into an upright sitting position with a slight bend in the arms.

Choosing the Right Bike Size

As we said earlier, the right bike size will depend on your measurements and the type of bike you want to buy. Take a look at the bike size charts below for each type of bike to help you find the right size bike for you and your riding style.

What Size Bike do I Need?

What Size Bike do I Need?

What Size Bike do I Need?

If you are in between sizes or at the top or bottom range of a sizing suggestion, then take a look at your reach or Ape Index measurement. If you have a positive measurement or longer reach, then go for the larger size bike.

Once you've bought the right bike and size for you, you may need to make some adjustments. This may mean lowering or raising the handlebars to get a comfortable reach or bend in the elbow. Or you may need to adjust the seat so that your tiptoes can comfortably reach the floor when you are stationary.

What Size Bike Does my Child Need?

Just like we've explained above, you should take your child's measurements and decide what type of bike is best for them. Once they are past toddler age and can cycle confidently without training wheels, your child's age may not be the best indicator of what size bike they need. Especially if they are particularly short or tall. One difference you will notice between children's and adults bike sizing is that children's bikes go by wheel size, rather than frame height. So, take a look at the size chart below to determine the right size bike for your child.

What Size Bike do I Need?


What if I'm between sizes?

If your measurements suggest that two sizes would work, it's up to you what to pick, but here's some things to consider:

For road bikes go with the smaller size as you can make a smaller sized frame seem bigger by raising the seat height.

For mountain bikes go with the larger size as you can fit a shorter stem to reduce the reach to the handlebars.

What if my child is between sizes?

It may seem tempting to buy a size or two up from your child's measurements, so they'll grow into it, but this isn't recommended, especially if your child is learning to ride a bike for the first time.

This isn't safe for a child as it's easier for them to overbalance and fall if the bike is too big. Not being able to feel comfortable whilst riding a bike too large for them may also knock their confidence.

If you're not sure which type of bike or frame size you need for yourself or your child, visit your local bike shop for some further assistance. You could also book a bike fitting to find the right bike for you and have it adjusted to suit your riding by a professional fitter.

Once you are ready to ride, don't forget to buy a bike rack so you can take your cycling adventures even further. If you are new to cycling you may be unsure about what to wear or how to pump or change your tyres. So, make sure you are prepared before you head out on a bike ride and enjoy your new wheels.

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