The circumference of a bike wheel is defined as the distance around the outside of the wheel. This distance includes the additional width that a tire brings to the wheel.
As you’re probably aware, wheel circumference is an important measurement for calibrating and ensuring the accuracy of a bike computer.
A bike computer, often referred to as a cyclometer, is a device that can provide detailed statistics on your bike rides, including the speed of your ride and the distance covered.
The majority of bike computers rely on counting a wheel’s rotations. So inputting the correct circumference is vital for accurate estimates of your speed and distance travelled.
To obtain the most accurate ride data possible, here are three easy ways to measure your wheel’s circumference.
For all of the below methods, ensure that your tire pressure is the same level you ride at.
At the bottom of the article, I’ve also included a bike tire circumference chart that you can use to verify the circumference of any bike tire.
Because cyclists have different preferences for tire pressure (PSI) and ride tires with varying amounts of wear, it’s essential to measure the circumference of your own tire.
Whilst a few millimetres of inaccuracy may seem marginal. However, over the duration of a long bike ride, any inaccuracy in tire circumference can significantly impact the accuracy of the data your bike computer provides.
The 3 Best Methods for Measure Bike Tire Circumference
Method 1 - Diameter of Wheel Multiplied By Pi
This method involves calculations you’ll probably want to use a calculator for.
- Measure the radius of your bicycle wheel, from the lowest point of tire contact with the floor to the centre of your wheel skewer or thru-axle.
- Multiply your wheel radius by 2 to find your total wheel diameter.
- Multiply the wheel diameter by Pi (diameter x 3.14).
- This final result is the circumference of your bike tire.
Formula for measuring bike wheel circumference: wheel diameter x 3.14 = wheel circumference.
Method 2 - Dot to Dot (tape to tape)
The dot to dot method is very simple but can be inaccurate if the steps below aren’t followed closely.
- Stretch your tape measure to around four meters in a straight line and lay it along the ground.
- Apply a dot of washable/non-staining paint to the centre of your bike tire.
- Roll your bike parallel to the tape measure making sure it travels in a straight line.
- Once two paint dots are on the ground, stop rolling and leave your bike to one side.
- Using your tape measure, measure the distance between the two paint dots—the distance between these two spots to determine your wheel circumference.
Method 3 - Wrap a Piece of String
- This method is significantly easier if you have an assistant to help you out. Otherwise, it can be quite fiddly!
- Take a ball of string and unwind it, so you have at least three meters unwound.
- Place one end of the string on the centre of the tire and hold it in place.
- Ask your partner to wrap the string around the tire, ensuring it’s wrapped in a straight line.
- Once the string returns to the starting position, either cut or mark the string where the two ends meet.
- Finally, use a tape measure to measure the total length of the piece of string.
- The length of this piece of string is the circumference of your bike tire!
Bike Tire Circumference Chart
If you could find your tire size information on the side of your tire, search it below, and the table will reveal the standard circumference of tires of that size.
This bike tire circumference chart is accurate and uses data on the circumferences of standardized tires sold worldwide.
It’s important to understand, though, that there will always be a slight difference in circumference for each rider.
Some cyclists prefer riding with a lower PSI, which decreases tire circumference, whilst others will be riding morn worn tires.
To ensure you enter the most accurate figure into your bike computer, I recommend using one of the methods above, as this will provide you with the most precise measurement.
After all, there’s no point in having a bike computer if it isn’t correctly calibrated.
| Tire Size | ISO Size | Circumference (meters) | Circumference (mm) |
|---|---|---|---|
| 700 x 18C | 18-622 | 2.07 | 2070 |
| 700 x 19C | 19-622 | 2.08 | 2080 |
| 700 x 20C | 20-622 | 2.086 | 2086 |
| 700 x 23C | 23-622 | 2.096 | 2096 |
| 700 x 25C | 25-622 | 2.105 | 2105 |
| 700C Tubular | - | 2.13 | 2130 |
| 700 x 28C | 28-622 | 2.136 | 2136 |
| 700 x 30C | 30-622 | 2.146 | 2146 |
| 700 x 32C | 32-622 | 2.155 | 2155 |
| 700 x 35C | 35-622 | 2.168 | 2168 |
| 700 x 38C | 38-622 | 2.18 | 2180 |
| 700 x 40C | 40-622 | 2.2 | 2200 |
| 700 x 44C | 44-622 | 2.235 | 2235 |
| 700 x 45C | 45-622 | 2.242 | 2242 |
| 700 x 47C | 47-622 | 2.268 | 2268 |
| 650 x 20C | 20-571 | 1.938 | 1938 |
| 650 x 23C | 23-571 | 1.944 | 1944 |
| 650 x 35A | 37-590 | 2.09 | 2090 |
| 650 x 38B | 40-584 | 2.105 | 2105 |
| 650 x 38A | 40-590 | 2.125 | 2125 |
| 12" x 1.75" | 47-203 | 0.935 | 935 |
| 12" x 1.95" | 54-203 | 0.94 | 940 |
| 14" x 1.50" | 40-254 | 1.02 | 1020 |
| 14" x 1.75" | 47-254 | 1.055 | 1055 |
| 16" x 1.50" | 40-305 | 1.185 | 1185 |
| 16" x 1.75" | 47-305 | 1.195 | 1195 |
| 16" x 2.00" | 54-305 | 1.245 | 1245 |
| 16" x 1-1/8" | 28-349 | 1.29 | 1290 |
| 16" x 1-3/8" | 37-349 | 1.3 | 1300 |
| 18" x 1.50" | 40-355 | 1.34 | 1340 |
| 18" x 1.75" | 47-355 | 1.35 | 1350 |
| 20" x 1.25" | 32-406 | 1.45 | 1450 |
| 20" x 1.35" | 35-406 | 1.46 | 1460 |
| 20" x 1.50" | 40-406 | 1.49 | 1490 |
| 20" x 1.75" | 47-406 | 1.515 | 1515 |
| 20" x 1.95" | 50-406 | 1.565 | 1565 |
| 20" x 1-1/8" | 28-451 | 1.545 | 1545 |
| 20" x 1-3/8" | 37-451 | 1.615 | 1615 |
| 22" x 1-3/8" | 37-501 | 1.77 | 1770 |
| 22" x 1-1/2" | 40-501 | 1.785 | 1785 |
| 24" x 3/4" Tubular | - | 1.785 | 1785 |
| 24" x 1" | 25-520 | 1.753 | 1753 |
| 24" x 1-1/8" | 28-540 | 1.795 | 1795 |
| 24" x 1-1/4" | 32-540 | 1.905 | 1905 |
| 24" x 1.75" | 47-507 | 1.89 | 1890 |
| 24" x 2.00" | 50-507 | 1.925 | 1925 |
| 24" x 2.125" | 54-507 | 1.965 | 1965 |
| 26" x 7/8" Tubular | - | 1.92 | 1920 |
| 26" x 1.25" | 32-559 | 1.95 | 1950 |
| 26" x 1.40" | 37-559 | 2.005 | 2005 |
| 26" x 1.50" | 40-559 | 2.01 | 2010 |
| 26" x 1.75" | 47-559 | 2.023 | 2023 |
| 26" x 1.95" | 50-559 | 2.05 | 2050 |
| 26" x 2.00" | 52-559 | 2.055 | 2055 |
| 26" x 2.1" | 54-559 | 2.068 | 2068 |
| 26" x 2.125" | 57-559 | 2.07 | 2070 |
| 26" x 2.35" | 58-559 | 2.083 | 2083 |
| 26" x 3.00" | 75-559 | 2.17 | 2170 |
| 26" x 1-1.0" | 25-559 | 1.913 | 1913 |
| 26" x 1" | 25-571 | 1.952 | 1952 |
| 26" x 1-1/8" | 28-590 | 1.97 | 1970 |
| 26" x 1-3/8" | 37-590 | 2.068 | 2068 |
| 26" x 1-1/2" | 37-584 | 2.1 | 2100 |
| 27" x 1" | 25-630 | 2.145 | 2145 |
| 27" x 1-1/8" | 28-630 | 2.155 | 2155 |
| 27" x 1-1/4" | 32-630 | 2.161 | 2161 |
| 27" x 1-3/8" | 37-630 | 2.169 | 2169 |
| 27.5" x 1.50" | 40-584 | 2.079 | 2079 |
| 27.5" x 1.95" | 50-584 | 2.09 | 2090 |
| 27.5" x 2.10" | 54-584 | 2.148 | 2148 |
| 27.5" x 2.25" | 57-584 | 2.182 | 2182 |
| 29" x 2.25" | 58-622 | 2.281 | 2281 |
| 29" x 2.1" | 54-622 | 2.288 | 2288 |
| 29" x 2.2" | 56-622 | 2.298 | 2298 |
| 29" x 2.3" | 60-622 | 2.326 | 2326 |
Conclusion - How to Measure The Circumference of a Bike Tire
The information found above should have helped you correctly calibrate your bike computer.
However, if for any reason you were unable to measure the circumference of your bike tire or didn’t understand something in this article, leave me a comment below, and I’ll get straight back to you.
If you’re looking for a more detailed guide on bike wheel sizes, you can read the complete guide on wheel sizing here.
As always, make sure you’re using a good quality bike lock to secure your bike when leaving it unattended.
Lock it or lose it.
Ciao for now!
3 Responses
my tire size is 29 X1.95 this size is not listed
Hi Francis,
For this tire size, the corresponding measurement in ETRTO is: 49.5 x 622
Unfortunately, where this tire size is quite uncommon, there isn’t a whole lot of information I can find about it.
Have you located any helpful information in the meantime?
Best,
James
My Specialized ebike tire is 29 x 2.6 (66-622) and I can’t find it in the chart. What is the rolling circumference in mm for my bike computer entry?