How to Measure Bike Wheel Size? 4-Step Guide

Measuring the bike wheel size is an exciting topic among many bike enthusiasts. This, however, can be a pretty confusing subject for new owners as it requires some level of knowledge.

This makes it important to update yourself and learn everything you can on the topic. It’s essential because information on measuring your bicycle wheel size can significantly help your biking experience.

Why is It Important to Measure Bike Wheel Size?

Many casual riders don’t associate any importance with the dimension of their bike and rim wheels. They assume it’s something without much value.

Yet, information on the bike frame size, rim diameter, bead diameter, and others can significantly help your biking experience.

In many cases, a rider will usually order a bike brand to suit them and make do with whatever bike tire that comes with it. Besides, they leave this task many times to the bike shop owner when it’s time for a repair or an upgrade on their tire.

However, knowledge of your bicycle tire is vital if you want to purchase new wheels. Yet, this can be quite challenging if you have no idea how to measure the required dimensions and every other parameter that relates to your wheel.

Many new tires come with sizes indicated on the outside. Sadly, with time, these numbers fade and become unreadable.

As a result, knowing how to measure your rim and wheel size is pretty important. The good news is that there’s a series of ways to determine the dimension of your bicycle wheels.

This article will explore simple ways through which you can measure the tire sizes on your bike.

How Do I Know My Bike Wheel Size?

In measuring the size of your tire, you’re after three primary parameters:

  • Bike tire diameter
  • Width
  • Circumference

Obtaining this measurement is pretty simple. All you need is a measuring tape with your paper and pen.

Step 1: Position your bike upright

Position your bicycle straight against a support (a kick stand will come in handy). Make sure it is firm and will not shift or wobble when taking the measurement.

Use a retractable metal tape as it makes the process easy.

Step 2: Measure the diameter of the tire

The following will guide you in measuring the wheel diameter of the tire:

  • Position your tape at the wheel’s center.
  • Extend your tape towards the tire’s edge in a straight line.

This is the radius. You get the diameter of the wheel by multiplying this value by two.

There is a different approach to get the ISO diameter, also known as the bead seat diameter.

The tape will extend from the wheel’s center to the inner edge of the wheel and not the outer. Multiplying this by two gives the value of the ISO diameter.

Step 3: Measure the width

All you need to do is place your tape on the ground. Put it across the tread of the tire in the same direction.

For measurement using the International Organization for Standardization (ISO), the width will be in millimeters and inches for the standard approach.

The size of the tire width varies among different bicycles. As a result, the width of mountain bike tires differs from that of road bikes.

Step 4: Combine the measurements

Bringing together both values, you can get the tire size. We have two measurements: the traditional and the ISO size.

  • For the traditional, you’ll have the diameter first followed by the width.
  • ISO sizes have the width first followed by the diameter.

How to Measure Circumference of Bike Tires?

Calculating the circumference of your tire is also possible if you can’t determine the radius. In this case, you will physically measure it.

You can use a rope or string to do so.

All you need to do is to wrap a ring along the external edges of your tire, not the rim from one side. The rim is the metal part of your tire that holds the tire.

Mark the string at the point where it meets the starting point. Get the length of the string on a tape measure.

This is the circumference you’re after.

Other Ways to Know the Tire Size

You can approach the seller of your bike for this info. There’s a big probability that sellers will have the specs of the bikes they have on sale.

Alternatively, you can also examine the markings on your wheel.

Most bikes do have their tire size listed right on it. BMX bikes, for instance, come with 20″ wheels.

If you have a new tire, there will be branding on them with a series of numbers. These figures reveal the dimension of the rim.

Assume that the labels read 26 x 1, for instance; This means that you have a wheel (not the rim) that is 26″ in diameter and a 1″ bike tire.

A 700C bike tire will come in a different format. You will have two sets of numbers: the first is the ISO number and the second is the traditional measurement you need.

Calculating Your Bike’s Wheel Circumference

You’ll need your bike’s circumference if you want to calibrate the GPS or speedometer. With some simple calculations, we can estimate the circumference. 

Circumference of a circle = πD

We are using a circle because your bike’s tire is round, so it assumes the shape of a circle.

Pi (π) is a constant with a value of 3.14 or 22/7.

With this, a BMX bike with a diameter of 20″ will have its circumference as 20×3.14, which gives 62.8 inches.

Similarly, a tire that reads 26 x 1 will have a circumference of 26×3.14, giving 81.64 inches.

We can either use this approach or calculate the circumference by using this formula below.

C =2πr; where π remains the same as above, and r is the radius

Using the same BMX bike as above,

C=2πr =2×3.14X10 = 62.80″

Conclusion

For everyone bothered with the question of determining the wheel sizes of a road bike, I believe this article will be of help.

You can determine the width, diameter, and circumference of your bike road tires in this guide, be it mountain bikes or adult bikes.

The steps described above are pretty simple, so I’m confident you’ll accurately determine your bike wheels’ dimension. This can guide your selection if you need to purchase new bicycle tires.

Note that where you position your tape matters, and your rim differs from your wheel’s outer part. a of this while taking the measurement.