What bike size do you need? Here's how to find out

Choosing the right size for your bike is vital to be able to enjoy it to the fullest without having to worry about possible future posture problems, but how do you know what size bike you need? Although this is an important issue, you will now see that it is easy to solve.

How to calculate the perfect size

The key to determining your bike size is your hip height or inner thigh measurement. To take the measurement we should stand with our back against the wall and our feet straight and slightly apart, place a book or a ruler between our thighs touching our inseam and measure the distance from the ground to the highest and furthest part of our body from the chosen object.

Once you have taken this measurement, you only need to multiply it by 0.54 to find your perfect mountain bike size in centimetres, or by 0.21 for inches. Most mountain bike manufacturers opt for the second option.

1. Stick to the wall with your back and heels straight.
2. Hold a book between your legs.
3. Measure the distance from the book (from the top) to the ground.
4. Multiply that measurement by 0.54 to get the size in cm, or by 0.21 to get the bike size in inches.

An example of how to calculate your bike size

For example, if our hip height or inseam measurement is 80, multiplied by 0.54 would equal 43.2, so our perfect size would be 43. In case the manufacturer of the bike we want measures the bike size in inches we would multiply 80 by 0.21, which would give us a result of 16.8. Our bike size in this case would be 17.

Mountain bike or road bike?

The above formula is valid for choosing the MTB size, i.e. a mountain bike. In case we want to buy a road bike, we should multiply the hip height or inseam measurement by 0.65. That is, taking the same example as in the previous paragraph, we would multiply 80 by 0.65 to know that our ideal bike size for road bikes is 52.

MTB or road bike size charts, by height or inner thigh

Now that you know how to measure the distance from the hip, here are some tables so that you know what size bike you need for both MTB and road.

MOUNTAIN BIKE size according to rider's height or inseam

HEIGHT	INSEAM	SIZE IN INCHES	SIZE
148-158 cm	70-74 cm	13"-14"	XS
158-168 cm	74-75 cm	15"-16"	S
168-178 cm	75-81 cm	17"-18"	M
178-185 cm	81-86 cm	19"-20"	L
185-193 cm	86-90 cm	21"-22"	XL

Road bike size according to rider's height or inseam

HEIGHT	INSEAM	SIZE IN CM	SIZE
155-160 cm	68-74 cm	47-48 cm	XSS
160-165 cm	71-76 cm	49-50 cm	XS
165-170 cm	73-79 cm	51-52 cm	S
170-175 cm	76-81 cm	53-54 cm	M
175-180 cm	78-84 cm	55-56 cm	L
180-187 cm	81-86 cm	57-58 cm	XL
187-190 cm	83-88 cm	59-60 cm	XXL
190-196 cm	86-92 cm	61-62 cm	XXL

Have you got the wrong size or is your bike too big or too small?

We cannot always choose the size of our bike, either because we are going to buy it second-hand, because it has been given to us as a gift, inherited, etc...

In this case we still have some alternatives to adjust the bike's measurements to our size. For example, we can play with the setback of the seat post, the placement of the saddle, the size of the stem or the number of spacers of the steering. If this is your case you can take a look at this other article where we explain it.

So, one way or another, we will be able to have a custom frame and a perfect MTB size. The bike size will be the right one to avoid physical problems and to perform to the maximum in each of our outings.