What Size Bike Do I Need?

When purchasing a bike, making sure you buy one in the right size is crucial, as riding a bike that is too big or too small for you can lead to back pain, knee pain, as well as poor performance.

However, there is so much discussion around this topic and things to consider that it can feel a bit overwhelming and confusing. But once you know the right formulas to use when calculating what bike size is for you, it takes some of the confusion and frustration out of the decision. 

These formulas are easy to follow, even if you’re not a math whiz.

Firstly, measure your leg inseam. You can do this either with your legs together or apart, as long as you measure the length of your leg on the inner side.

It’s important to remember that when using different methods you will get different sizes, but measuring your leg inseam is the most accurate.

To figure out what size mountain bike you should buy, multiply your leg inseam by 0.685 and this will give you your frame size in centimeters.

For road bikes, you multiply your inseam by 0.70 and this will also give your frame size in centimeters.

An example for a road bike would be that if your leg inseam is 70cm, then you multiply 70cm by 0.70 to get 49cm.

While this is a simple formula to follow, for reassurance it is also advisable to ask the seller of the bike what size they would recommend.

They usually have size guides to help you and should be able to answer any further questions you have.

For a more advanced fitting, you can also consider different bike measurements, such as the seat tube length, standover height, top tube length, stack, reach, head tube length, and many more measurements, but these are certainly not a requirement to find the right bike size for you.

How long is an adult bike?

The average adult bike is 69” (or 175cm) long. The handlebars on road bikes can vary from 15 to 18 inches (or 38-46cm). While on mountain or hybrid bikes they are usually 20 to 24 inches (or 51-61cm).

Adult bikes are measured by their frame size, and most manufacturers now measure the frame from the center of the crank axle to the top of the seat tube.

Road bikes are usually measured in centimeters while mountain bikes are usually measured using inches.

Meanwhile, bikes for children are measured by wheel size rather than frame size. Bikes with smaller wheels are lighter and easier for smaller children to handle, but as they grow riding these bikes will be more difficult.

The wheel sizes for children range from 12-inch balance bikes up to 25 or 26-inch junior bikes.

What height is a 27.5” bike for?

27.5” is the diameter of the wheel, and 27.5” wheels hit the sweet spot between agility and speed.

As they are smaller than a 29” but bigger than a 26” this makes the bike easier to accelerate and operate, and also to throw around - perfect for ‘jibbing!’

Bikes that are built around 27.5 wheels accommodate this by reducing the chain-stay length, design it around a shorter stem, and optimize the rear suspension for a more fun ride.

If you are mainly taking your bike to the bike park and not on long, epic rides or races and are not willing to sacrifice handling capabilities for more speed and rollover, a 27.5” inch bike may be the one for you!

For mountain bikes, the recommended height to ride a 27.5” wheel would be 5’9” and 6’0.”

What size bike do I need if I’m 5’10”?

It’s important to remember that bikes size differently depending on what type of bikes they are, and a mountain bike is no exception.

Most mountain bike manufacturers use classic Small, Medium, and Large sizing.

Usually, the bike frame size is the only thing that varies as you go between sizes. Things like wheel size, suspension, and relative geometry number remain the same.

However, some manufacturers will alter the wheel size and suspension travel across the sizes of the same model.

The traditional method for bike sizing is the seat tube length. But now mountain bikes come in so many different shapes that it’s not so important to find the seat tube length.

Most mountain bikes focus on an extremely low standover height, so the traditional method of standing over the bike flat-footed doesn’t work anymore either.

This is why mountain bike manufacturers go by the Small, Medium, Large size guide that corresponds roughly with your height.

A size chart is the best place to look when trying to choose the right size mountain bike, especially the size chart that is specific to the brand.

This is because every brand has differences in its geometry and design philosophy.

If you’re between 5’7” and 5’10” the recommended frame size for a Mountain bike would be a Medium. This is 17-18 inches or 43-47cm.

Or, if you’re between 5’10” and 6’0” then the recommended size would be Large, which is a frame size of 56cm.

Meanwhile, if you’re 5’10” the recommended size for a road bike would be Large with a frame height of 56cm.

However, if you happen to fall between bike sizes, you can always choose a Medium or Large frame if the bike is adjustable.

If you have long arms though, then you may want to opt for a larger frame as this will be more comfortable and give you more control of the bike.

What size bike should a 5’2” woman ride?

Generally, the recommended road bike size for a 5’2” woman would be XS and the frame size would measure 47-49cm.

Meanwhile, for a mountain bike, it would be Small with a frame size of 15-16 inches.

However, every person is different so fit requirements will vary from person to person. For example, if you have shorter legs - whether generally or in relation to your height - then the standover height of a frame is even more important.

In this case, it would be better to ride a smaller frame or a frame with more compact geometry.

You may also want to compensate with a longer stem, an increased saddle setback, or both.

As mentioned previously, if you’re unsure or if you would like further clarification then it’s always wise to consult a professional bike fitter before investing in a bike that is uncomfortable or difficult to ride.

They can take your individual requirements into account and make recommendations on appropriate sizing and fit.

What size bike should a 5’6” woman ride?

Generally, the recommended road bike size for a 5’6” woman would be Medium with a frame size of 53-55cm.

Meanwhile, the recommended mountain bike size for a 5’6” woman would be a Medium with a frame size of 17-18 inches.

Many women find that bikes built specifically for women suit them better, while other women prefer unisex frames.

The designs for womens’ bikes usually take into consideration women’s narrower frames, but for those who have a larger body type or prefer a bigger bike, a unisex bike will still be suitable.

Common benefits of a women’s bike include a women-specific finishing kit, such as a women-specific saddle, and that the ranges tend to run to smaller sizes to accommodate smaller riders.

However, some women’s bikes are based around a unisex frame but also come with a women-specific finishing kit.

For example, Liv Cycling and Canyon boast a bespoke geometry that is designed around women-only body dimension data to give you a more accurate idea of what size is right for you.

What size bike should I get if I am 5’2”?

Much like mountain bikes, some road bike manufacturers have started using Small, Medium, and Large sizing for road bikes.

Not only that, but they have also started to change the road bike geometry by adding a more sloping top tube like a mountain bike.

This is because sizing conventions like this gives riders a wider scope for size and accommodate for a wider range of riders. A good example of this is the Cannondale Synapse and GT Grade. 

Generally, though, the recommended size for a road bike if you’re 5’2” would be an XS with a frame size of 48cm. However, if you require an XS size then you, unfortunately, need to forfeit the 700c wheels for 650bs.

As we have already discussed, sizing a mountain bike is different from other bikes - even with the changes being made to road bikes to replicate mountain bikes.

This is because mountain bikes are used for traversing rocky terrain such as, well, mountains. Therefore, you require a ride that fits your body.

Generally, though, the recommended size for a mountain bike if you’re 5’2” is a frame size of 15-16 inches.

One of the things to look out for when riding your mountain bike and deciding whether you have the right fit is pedaling.

When you are pedaling and your foot reaches the bottom of the stroke, then you should only see a slight bend in your leg.

Ideally, your leg should be 80 to 90 percent extended so you can effectively work your leg muscles to climb hills and ride across rough terrain.

Although mountain bikes have a pretty standard size guide, their geometry is different from other bikes and you should pay attention to how you ride, especially because riding a mountain bike is different from riding a road bike.

Take notice of the top tube length, your stand-over clearance, the seat height, and the reach.

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