What size bike should I buy?

What size bike should I buy?

Wondering what size bike is right for you or your child? In the following article, Canberra Cyclist editor Julia Widdup demystifies women’s and kids bike sizing and models.

Is there a difference between women’s and men’s bikes?

Nearly all the big bike brands make what they call ‘unisex’ bikes; bikes that they say are designed for all riders.

A lot of brands also make women’s-specific bikes. Often these are mostly the same as the unisex bikes but with different contact points, such as the saddle and handlebar, which will be chosen to suit women better.

When bike shops and brands talk about bike size, they are specifically referring to the size of the frame, so bike size and frame size are often used interchangeably.

Currently, there is no industry standard for sizing bikes, so choosing the correct frame size for you can be confusing, especially since recommended frame sizes vary between manufacturers, models and disciplines.

Bike frame sizes are most commonly listed in centimetres (e.g. 48 cm, 54 cm), inches (e.g. 17 in, 19 in) and in sizes such as small, medium and large.

Generally adult bike sizes are determined by the height of the rider. If you sit between sizes, it’s worth trying both and seeing which one you feel more comfortable on.

Most bike manufacturers have their own size guides for each of the bikes they stock, again using rider height to determine the right size. Test riding a bike before you make a purchase is a quick and easy way to tell if you’re in the right ballpark for size.

Do you need a women’s bike?

Many women find that a women’s-specific bike suits them well, while others get on fine with unisex frames.

Women’s bikes typically include women’s fittings such as a women’s bike saddle and their ranges tend to run to smaller sizes to suit smaller riders. Some women’s bikes are based around a unisex frame with women’s-specific finishing kit, while others have a bespoke geometry designed around women-only body dimension data.

Bikes are sized as small, medium, large, etc (usually mountain bikes and some hybrid bikes), or numerically as centimetres or inches (e.g. 54cm, 17in, etc). Sizing is not consistent across brands so don’t expect one brand’s medium to feel exactly the same as another’s.

Most brands have an online size guide that will recommend a size based on your height, or other measurements such as your inner leg length. Online-only sellers, such as Canyon, will often ask you for a set of body measurements, for example, arm length, to help you find the right size. If buying online, check whether the retailer will allow you to swap components such as the stem and handlebars after purchasing, or whether you’ll have to purchase these separately if needed. Although you can make small adjustments to fit by changing components later, the frame size will be fixed. Take your time and don’t buy a frame that’s the wrong size just because it looks like a bargain.

Every person’s anatomy is different, so everyone will have different fit requirements. For example, if you have short legs (in general or relative to your height), the stand-over height of a frame is important. It may be preferable to ride a smaller frame, or a frame with a more compact geometry, and compensate with a longer stem, increased saddle setback or a combination of both.

Whatever approach a brand has to designing women’s bikes, there are usually a few things they have in common:

  • Smaller sizes: Small, X-Small and XX-Small cater for smaller riders. Sometimes these are the small sizes of the men’s/unisex bike, other times they’re a dedicated women’s frame with a unique geometry.
  • Lowered top tube: This mostly applies to hybrid or commuter bikes, particularly Dutch or ‘sit up’ bikes. They have a lower or sloping top tube which means it’s easier to stand straddling the frame, making it easier to get on and off.
  • Women’s saddle: Women’s bikes usually come with a saddle designed to be comfortable for female riders.
  • A shorter reach: This refers to the distance from the saddle to the handlebar. Bikes with a frame designed for female riders will sometimes have a shorter reach compared to equivalent men’s or unisex models. This sometimes results in a more upright position for the rider.
  • Shorter crank arms: For riders with shorter legs, shorter crank arms (the part linking the pedals to the spindle around which they move) reduce the stretch that the leg needs around the pedal stroke, which reduces strain and makes pedalling easier. Shorter cranks can also be pedalled faster.
  • Narrower handlebar, shallower drops on road handlebar: Narrower handlebars are designed to suit narrower shoulders, and the shallower drop on road handlebars means a shorter reach from the seat to the bar.
  • Lighter shock tune: Mountain bikes that feature suspension will have this set up to accommodate the on-average lighter weight of female rider.

Once you have a bike, it’s possible to adjust the fit to make it even better, which is important if you’re going to be riding it a lot because small niggles can turn into big niggles over a long bike ride.

What about your child’s first bike or replacement bike?

Children’s bikes are sized according to their wheel size, not their frame size like adult bikes. You also need to consider is the frame weight. A lightweight frame that places the child in a stable, comfortable riding position is easier to pedal and more enjoyable to ride. Bikes made with alloy frames are typically more expensive than bikes with steel frames but they are lighter, easier to ride, as well as being less prone to rust. The height of the child is more important than the child’s age, however, for simplicity this guide (right) refers to the suitability of the bike relative to approximate age groups.

Children’s bike options:

  • Balance bikes

A perfect introduction to bikes is a balance bike. This is a two-wheeled bike without pedals that allow children to sit and coast and helps them develop the balance and skills required to ride a bicycle. They have a 12 inch wheel and are suitable for children up to 2 years old 

  • 78-94 cm – 12 inch bikes

These are generally suitable for children 2 to 4 years old. These bikes come with training wheels, and may feature a rear push steerer so the child can be assisted or directed when needed.

  • 84-112 cm – 16 inch kids bike

16 inch bikes are generally suitable for children aged 3 to 6 years old. Typically bikes this size will have training wheels and no gears. Around this age children may not have developed a lot of the strength required for riding, so the bike’s weight will be an important consideration.

For older children you may want to consider a 16 inch BMX for a stronger, heavier duty bike.

  • 108-129 cm – 20 inch kids bike

20 inch bikes are generally suitable for kids aged 6 to 10 years. It is also the standard size for a BMX wheel.

They both have no gears and the 20 inch kid’s bike and BMX share a lot of similarities. The main difference between the two is that a kid’s bike will be lighter and easier to ride, and a BMX will be heavier and more durable.

Kid’s bikes are designed in a mountain bike style, whereas BMX are designed more for street and skate park riding. A kid’s bike may be a better option if the child is still learning to ride, while a BMX will be more suitable if the child is already confident – or if they have a tendency to be rough with things.

  • 120-148 cm – 24 inch kids bikes

24 inch geared bikes can suit children aged 8 to 13 years old. 24 inch bikes are designed in a mountain bike style and have features like gears and suspension forks. 24 inch is the second largest of the kids bikes. For taller kids, the next progression would be onto a 26 inch kids bike or an extra small adults mountain bike.

145-160 cm – 26 inch kids bikes

26 inch mountain bikes are suited for kids that are 9 to13 years old. 26 inch bikes typically have gears and suspension forks. 26 inch bikes are the largest of kids bikes before going to an extra small adult bike. Taller kids above 148 cm now have an option to go for a 26 inch kids bikes as opposed to a small adult’s frame. The junior frame style features an easy reach brake lever and other child-friendly features, making them a preferred choice over an extra small adult’s frame for children.

[ngg src=”galleries” ids=”13″ display=”basic_thumbnail”]References



Women’s bike size guide – https://www.youtube.com/watch?v=0pSMr8bnjd8 How to find the right size bike

Find the right mountain bike, hybrid and road frame size for you, by Faye Sander.