The right bike size is one of the most important things when buying a bike online. Even if the bike looks good, is the right price and has quality parts, it will not be comfortable if the frame is too small or too large.

A bike that is too small can strain your knees, back and hands. One that is too large is harder to handle, particularly in town, on forest tracks, or for a child learning to ride.

This guide gives indicative bike size charts by height: for adults, for children, and for MTB, hybrid and city bikes.

The short answer: what size bike to choose by height

If you want a quick orientation, start with this chart.

Height	Common frame size	Size marking
150–160 cm	14–15″	XS / S
160–170 cm	15–17″	S / M
170–180 cm	17–19″	M / L
180–190 cm	19–21″	L / XL
190+ cm	21″+	XL / XXL

This is an indicative chart. The exact size depends on the type of bike, the manufacturer’s geometry, the length of your legs and your riding style.

If you fall between two sizes, it is often worth choosing:

Situation	What to choose
You want a more manoeuvrable bike	The smaller size
You want a more stable bike for longer distances	The larger size
You are choosing a bike for a child	Not oversized, but right for now
You are choosing an MTB for the woods or active riding	Slightly smaller is often more comfortable
You are choosing a city bike for comfort	The more comfortable, stable size usually suits

1. Why bike size matters so much

Bike size decides more than whether you can put a foot down. It affects the whole feel of riding:

• whether sitting on it is comfortable;

• whether your back gets tired;

• whether your knees hurt;

• whether the bike is easy to handle;

• whether braking and manoeuvring feel safe;

• whether it suits longer routes.

The right size matters especially when buying online, because you cannot sit on the bike first. So you need to know at least three things:

• your height;

• your inside leg length, if you can measure it;

• what type of bike you are choosing.

2. How bike size is marked

Bike sizes are marked in several ways.

Adult bikes

Adult bikes are usually marked:

• with letters: XS, S, M, L, XL;

• in inches: 15″, 17″, 19″, 21″;

• in centimetres: 48 cm, 52 cm, 56 cm;

• and sometimes only by the manufacturer’s own chart.

A hybrid may be marked size M, an MTB 17 inches, and a road bike a 54 cm frame.

Children’s bikes

Children’s bikes are usually chosen by wheel size rather than frame size.

The usual children’s sizes are:

• 12″;

• 14″;

• 16″;

• 18″;

• 20″;

• 24″;

• 26″.

For children what matters is not age alone but height, leg length, and whether they can safely reach the ground.

3. Adult bike size chart by height

This chart gives a general orientation when choosing an adult bike: hybrid, city, MTB or leisure.

Height	Frame size in inches	Letter size	Who it usually suits
150–160 cm	14–15″	XS / S	Shorter adults and teenagers
160–170 cm	15–17″	S / M	Shorter to average height adults
170–175 cm	17–18″	M	Average height adults
175–180 cm	18–19″	M / L	Average to taller adults
180–185 cm	19–20″	L	Taller adults
185–190 cm	20–21″	L / XL	Tall adults
190–200 cm	21–23″	XL / XXL	Very tall adults

Important: an M from one manufacturer is not an M from another. One brand’s M can feel like another’s L. Always check the size chart for the specific model.

4. MTB size by height

An MTB, or mountain bike, is usually ridden on forest tracks, gravel, rough ground and generally more actively. That makes handling especially important.

An MTB that is too large is harder to control on forest trails. One that is too small can be uncomfortable over longer distances.

MTB frame size chart

Height	MTB frame size	Letter size
150–160 cm	13–15″	XS / S
160–170 cm	15–16″	S
170–175 cm	16–17″	S / M
175–180 cm	17–18″	M
180–185 cm	18–19″	M / L
185–190 cm	19–21″	L
190+ cm	21–23″	XL

When to choose the smaller MTB size

A smaller MTB frame can be better if:

• you will ride forest trails;

• you want more manoeuvrability;

• you like riding actively;

• you are between two sizes;

• you need the bike to be easier to handle on rough ground.

When to choose the larger MTB size

A larger MTB frame may suit if:

• you will ride longer distances;

• stability matters more;

• you will ride more gravel than technical trails;

• you have longer legs or arms.

5. Hybrid bike size by height

Hybrids are one of the most popular choices, because they suit the city, cycle paths, light gravel and weekend rides.

With a hybrid the point is to balance comfort against efficient pedalling.

Hybrid frame size chart

Height	Hybrid frame	Letter size
150–160 cm	14–15″	XS / S
160–170 cm	15–17″	S / M
170–175 cm	17–18″	M
175–180 cm	18–19″	M / L
180–185 cm	19–20″	L
185–190 cm	20–21″	L / XL
190+ cm	21–23″	XL

Hybrid: what to choose if you are between two sizes

If you fall between two sizes, the choice depends on use:

If you want…	Choose…
A more comfortable, relaxed ride	The larger size
Easier handling in town	The smaller size
Longer routes	The larger size
Frequent stopping and manoeuvring	The smaller size

For example, at 178 cm choosing a hybrid, both M and L will often work. If you ride in town, stop often and want manoeuvrability, take the M. If you ride longer distances, the L may suit.

6. City bike size by height

With a city bike what matters most is comfort, a stable riding position and easy handling. You do not need the sportiest size; what you need is to get on and off easily, stop easily, and ride with a bag or your daily things.

City bikes often have a lower frame, a more upright position and practical extras: mudguards, a rack and lights.

City bike size chart

Height	City bike frame	Letter size
145–155 cm	13–14″	XS
155–165 cm	14–16″	S
165–175 cm	16–18″	M
175–185 cm	18–20″	L
185–195 cm	20–22″	XL

How is a city bike different where size is concerned?

On city bikes it is often not only frame size that matters, but also:

• whether it is easy to get on;

• whether sitting more upright is comfortable;

• whether your foot safely reaches the ground when you stop;

• whether the handlebar is not too far away;

• whether the bike is not too heavy for everyday use.

If you are choosing a city bike for daily use, comfort usually matters more than sporting precision.

7. Children’s bike size by height

A child’s bike has to be chosen carefully. A bike bought to grow into can be unsafe, harder to control and less enjoyable to ride.

The child has to be able to:

• sit comfortably;

• reach the handlebar;

• to brake safely;

• control the bike;

• reach the ground when needed.

Children’s wheel size chart by height

Child’s height	Age as a guide	Wheel size
85–100 cm	2–4 m.	12″
95–110 cm	3–5 m.	14″
100–120 cm	4–6 m.	16″
115–130 cm	5–8 m.	20″
125–145 cm	7–11 m.	24″
140–160 cm	10+ m.	26″

The ages in the chart are only a guide. Two children of the same age can be very different heights, so go by height and by how confident the child is on the bike.

Why not to buy a child an oversized bike

A common mistake is to buy a bigger bike so that it lasts longer. But an oversized bike can be a problem for a child:

• harder to stop;

• harder to turn;

• harder to set off on;

• a greater risk of falling;

• and the child may become afraid of riding.

A bike that fits now beats one that will theoretically fit in two years.

8. Wheel size: what 26″, 27.5″, 28″ and 29″ mean

Frame size and wheel size are not the same thing.

Frame size tells you how big the bike’s structure is for the rider.
Wheel size tells you the diameter of the wheels fitted to it.

On adult bikes you usually meet these wheel sizes:

Wheel size	Where it is usually used
26″	Children’s and junior bikes, some MTBs, smaller frames
27.5″	MTB, all-round bikes, manoeuvrability
28″	City, hybrid, trekking, road and gravel bikes
29″	MTB, better rollover, stability

Does wheel size depend on height?

Partly, but not directly.

A rider of 160 cm and one of 185 cm can both ride 28″ wheels, provided the frame size is right. So when choosing an adult bike, frame size matters more than wheel size alone.

With children’s bikes it is the other way round: wheel size usually comes first.

9. How to measure your inside leg

If you want to choose a size more precisely, it is worth measuring your inside leg.

How to measure?

• Stand barefoot against a wall.

• Stand with your feet about 15-20 cm apart.

• Take a book and press it up between your legs as if it were a saddle.

• Measure from the floor to the top of the book.

• That figure is your inside leg length.

This measurement helps you judge whether the frame will be too tall and whether standing over the bike will be comfortable.

10. Examples: which size to choose

Example 1: 165 cm tall, hybrid bike

At 165 cm choosing a hybrid, you would usually be looking at S or M, roughly a 15-17″ frame.

If you want manoeuvrability in town, take the S.
If you ride longer distances and have longer legs, the M may suit.

Example 2: 178 cm tall, MTB

At 178 cm an M size MTB usually suits, roughly a 17-18″ frame.

If you ride forest trails and want lively handling, go for 17-18″.
If you ride more gravel and want stability, consider 18-19″.

Example 3: 183 cm tall, city bike

At 183 cm an L size city bike usually suits, roughly a 19-20″ frame.

On a city bike what matters is getting on easily, sitting upright and stopping safely. If the frame is very tall, look for a model with a lower one.

Example 4: a child of 118 cm

A child of 118 cm usually suits a bike with 16″ or 20″ wheels.

If the child is not yet confident, take the smaller, easier-to-handle option. If they ride well already and have longer legs, 20″ is worth considering.

Example 5: 190 cm tall, hybrid bike

At 190 cm you will usually need an XL, or a 21-23″ frame.

But look at the geometry too. Long legs may call for a larger frame. With longer arms, or if you want a sportier position, the reach to the handlebar matters as well.

11. What to do if you are between two sizes

This is very common. At 175 cm, say, the chart suggests both M and L could work.

In that case weigh up not just your height but how you will use the bike.

If you are between sizes and…	Usually choose
You will ride in town	The smaller size
You want a comfortable, relaxed ride	The larger size
You will ride forest trails	The smaller size
You will ride longer routes	The larger size
You have shorter legs	The smaller size
You have longer legs	The larger size
You are choosing a bike for a child	The smaller size, the one that fits now

The point is not to take the bigger one on the chance it works out, but to choose the one that suits how you will actually ride.

12. Sizing mistakes worth avoiding

1. Choosing by wheel size alone

On adult bikes frame size is what counts. 28″ wheels do not mean the bike fits everyone.

2. Buying a child a bike that is too big

A bigger bike is not a better investment for a child if it becomes unsafe and uncomfortable.

3. Assuming all M sizes are the same

An M differs between manufacturers. You have to look at the chart for the specific model.

4. Ignoring the type of bike

MTB, city, hybrid and road bikes can have very different geometry even when the size marking is the same.

5. Not allowing for your riding style

The same height does not mean the same choice. One rider will want the more stable size, another the more manoeuvrable one.

13. How to tell the bike is the right size

A bike of the right size should feel natural and safe.

Signs the size is right:

• you can reach the handlebar comfortably;

• your knees are neither too bent nor too straight;

• you do not have to stretch forward too far;

• you can stop safely;

• the bike handles easily;

• after a ride you feel no real discomfort in your back, knees or hands.

Signs the bike is too small:

• your knees are very bent;

• you sit cramped;

• the handlebar feels too close;

• pedalling comfortably is hard;

• your legs tire quickly.

Signs the bike is too large:

• getting on and off is awkward;

• the handlebar is too far away;

• manoeuvring is hard;

• you feel unstable;

• stopping safely is hard.

14. What to tell us when asking for advice

If you are buying online and unsure about size, send the seller this information:

• your height;

• your inside leg, if you know it;

• what type of bike you are looking for;

• where you will ride: in town, on gravel, in the woods, on longer routes;

• whether you want a sporty or a comfortable position;

• whether you will have to carry the bike up stairs;

• whether you have a previous bike and what size it is;

• what budget you have in mind.

With those answers the right size can be picked far more accurately.

15. Frequently asked questions

What size bike suits someone 170 cm tall?

At 170 cm an S or M usually suits, roughly a 16-18″ frame. The exact choice depends on the type of bike: an MTB is often closer to 16-17″, a hybrid 17-18″.

What size bike suits someone 180 cm tall?

At 180 cm an M or L usually suits, roughly an 18-20″ frame. For an MTB where you want manoeuvrability, the M may be right; for a hybrid or city bike over longer distances, the L.

Does a 28 inch bike suit every adult?

No. 28″ usually refers to the wheel size, not the frame. On an adult bike it is the frame size that matters. Two bikes with 28″ wheels can have completely different frames.

Should you buy a child a bike to grow into?

Better not. An oversized bike can be unsafe and hard to control. The child has to reach the bars and brakes and control the bike now, not in a year’s time.

How do you choose between M and L?

If you are between M and L, choose by use. For town, manoeuvrability or an MTB, M is often more comfortable. For longer distances, stability or a more relaxed ride, L may suit.

Does frame size depend on gender?

What matters is height, leg length and comfort, not gender. Some women’s bikes have a lower frame or different geometry, but the size still has to be chosen from the rider’s proportions.

What do bike sizes S, M and L mean?

S, M and L are approximate size labels. S usually means a smaller frame, M a medium one and L a larger one. The exact dimensions depend on the manufacturer, so always check the chart for the specific model.

What wheel size suits a child?

Wheel size for children is usually chosen by height. A child of 100-120 cm often suits 16″ wheels, 115-130 cm 20″, and 125-145 cm 24″. What matters is that the child can control the bike safely.

In short: the right size depends on height, leg length and use

Bike size is worth choosing not by eye but against a few clear criteria:

• height;

• inside leg;

• type of bike;

• riding style;

• the manufacturer’s size chart;

• whether you want more comfort, more stability or more manoeuvrability.

For adults frame size usually matters most, for children wheel size. If you are between two sizes, decide by where and how you will ride.

Need help choosing a bike size?

Write to us with

your height, inside leg, budget and where you will ride: in town, on gravel, on forest trails, to work, with the family or on longer routes.

We will help you pick the right frame size and select bikes that genuinely suit your height and your riding.

Send us your height, budget and where you will ride, and we will help you find the right bike.