How to measure your Bicycle Wheel before converting to an E-Bike

LEED Mechanic measures a bicycle wheel to convert the bike to electric with an e-bike kit.

When you purchase a new electric bicycle conversion kit from Leeds Bicycle Solutions, one of the first questions our checkout system will ask you is “What is your wheel size?”



While this may seem like a simple question, it can cause confusion for many people, and with good reason. There are so many different wheel sizes and different ways of measuring bicycle wheels that you might not be sure what size you should order for your bike. This is extremely important since we customize your electric bike wheel to your bike wheel size.

We have many customers who inadvertently order the wrong size, causing paperwork issues, extra shipping charges, which delays the amount of time it will take you to get your e-bike kit installed on your bike so that you can go party! Part of the confusion is the fact that many people misunderstand what is meant by “wheel size.” The electric bike wheel size is the diameter of the wheel PLUS the width of the tire. For example, a standard 20″ bicycle wheel has an actual diameter of 16.5,” but after you put a 20″ x 1.75″ tire on the wheel, the total diameter actually measures 20.” Confusing, right?



If your bicycle wheel does not show the measure, then here are some simple ways to measure your wheel, and ensure you get the RIGHT electric bike wheel, the first time we ship it.

1. CHECK THE LABELING ON YOUR TIRE. This is the easiest and most common way to determine the rim size you need.  On the sidewall of most commercially branded tires you will find a series of numbers which tell you the size of your rim. For example, it might read “26 x 1.5″”. This indicates that the wheel is 26″ total, with a 1.5 inch tire.  On a 700c, the numbers on the tire would look more like this:



When working with 700c tires, I usually tell my customers not to worry about the first set of numbers at all. The first series of numbers is the “ISO number,” which is basically just a fancier and more complicated way of telling you to look at the second set of numbers.

What you should be looking for is the second line that says “700 x 23c.”  But don’t worry if you don’t see any numbers at all. Sometimes the bike tire numberes become worn and unreadable over time. You can still measure the size yourself using the next method.

2. PHYSICALLY MEASURE THE DIAMETER OF YOUR WHEEL. Remember, this is measuring the rim PLUS the bicycle tire. This can be explained in 3 simple steps.

  1. Step 1. Hold your bike, or tire/rim combination in place.  Or, better yet, have a friend hold it for you.
  2. Step 2. Stretch a measuring tape across the length of the rim AND tire, placing the tape right on top of the axle in order to measure the wheel at it’s widest point.
  3. Read the number at the far end of your tire. This should be your diameter. You want to measure in inches for every bike size except a 700c, this would be measured in millimeters. (A 700c rim should be 622mm, measured with the tire should give you 700mm).

3. TAKE IT A STEP FURTHER AND MEASURE THE CIRCUMFERENCE OF YOUR bike WHEEL. “Well, now why would I want to do that?,” you may ask. It’s true that the circumference won’t tell you what wheel size to choose, but this can be an important measurement for another reason. So, we thought we ought to mention it.

If you have purchased one of our bike computers, or you already own some form of bicycle speedometer, odometer or GPS system, you will want to determine this measurement in order to properly calibrate that device. Just as your car’s speedometer and odometer will provide inaccurate data if you change the size of its wheels, bicycle components must also be set based on the size of your tires. Don’t fret. You still have a few different options on how to find circumference of your bike wheel.

  1. This requires some arithmetic. If you have already determined your wheel’s diameter, the circumference can be determined by multiplying that number by pi. Pi is equal to 3.14, so the circumference of a 26 inch tire is 26 x 3.14, which equals 81.64 inches. However, if math isn’t your forte, you can try the next option.
  2. Wrap a tape measure or string around the outside edge of your wheel. If you want to measure correctly in order to calibrate your bike computer, then you would want to place the tape measure around the tire. Mark the string or tape measure at the spot where it reaches back to it’s starting point and measure it’s length to determine the circumference.circum-IMG_6397sm
  3. Add a dot of wet paint to a spot on your bicycle’s tire tread. Carefully push the bicycle in a straight line for at least 2 rotations, ensuring the paint marks the ground twice.  Measure the ground from the first spot of paint to the next in order to determine the tire’s circumference.


Choosing an electric bike conversion kit should be a fun and easy experience. Hopefully, by eliminating the stress of not knowing the proper e-bike wheel size to choose, you can focus on bigger decisions, such as what size Lithium-Ion E-Bike Battery is best for you, or what other electric bike accessories you might need. As always, we are here to help with any questions you may have. You can email us at 24/7 or call us at (866) 933-8716 between 9am and 5pm M-F MDT.