By Caleb MorganUpdated November 2026
A tyre size chart for bikes lets you read the numbers printed on your tyre sidewall and match them to the right replacement. Once you know how to decode the markings, you can buy the correct tyre the first time and avoid fitting problems. This guide walks you through the main sizing systems, how to measure your current tyre, and what to check before you order.
Understand the Three Main Sizing Systems
Bike tyres are labeled in one of three common ways, and they often appear together on the same sidewall. The most useful number for fitting is the ETRTO code, which is the international standard. It looks like 47-622, where the first number is the tyre width in millimeters and the second is the bead seat diameter in millimeters.
Shopping for one? See our guide: 5 Best Road Bike Shoe Size Charts (2026): Expert Picks.
Older tyres and many city and cruiser bikes use inch sizes, such as 26 x 1.95 or 700 x 35c. Road bikes sometimes show French sizes like 700 x 23 C, where the last number is a width in millimeters for a 700c wheel.
How to Measure Your Current Tyre
If the sidewall is worn or unreadable, you can measure the tyre directly. Use a ruler or caliper and follow these steps:
- Deflate the tyre fully and remove it from the rim if you can.
- Measure the tyre width across the widest part of the tread with the tyre inflated to its normal pressure, in millimeters.
- Measure the bead seat diameter by checking the rim diameter, or match it to the wheel size printed on the rim or hub.
- Convert your numbers to ETRTO format if the chart you use lists that system.
Match the Tyre to Your Wheel and Rim
The tyre must match the wheel’s bead seat diameter exactly. A 26-inch tyre will not fit a 27.5-inch rim, even if the width looks similar. Check your rim markings first, then choose a tyre width that your rim and frame can accommodate. Most rims list an acceptable width range, and most frames list a maximum tyre clearance.
| Common bike type | Typical wheel size | Typical ETRTO code |
|---|---|---|
| Road bike | 700c | 622 (e.g., 25-622) |
| Mountain bike | 29-inch | 622 (e.g., 54-622) |
| Mountain bike (older) | 26-inch | 559 (e.g., 47-559) |
| Hybrid or city bike | 700c | 622 (e.g., 38-622) |
For a deeper look at frame and wheel fit, see Women's Bike Wheel Size Chart: Find Your Right Fit (2026) and Wheel Size Chart for Bike Computer: Set the Right Tire Circumference.
Choose Width for Your Riding Style
Once the diameter is correct, width is your main choice. Narrower tyres roll faster on pavement, while wider tyres absorb bumps and give more grip on loose surfaces. Hybrid and commuter riders often do well with widths around 35 to 45 mm, and trail riders may prefer wider mountain tyres. If you are new to cycling, Women's Hybrid Bike Size Chart: How to Find Your Right Frame Size can help you confirm the frame fit that goes with your tyre choice.
Check Clearance Before You Buy
A wider tyre needs more room between the tyre and the frame or fork. Look for the maximum tyre size listed in the frame manual or on the manufacturer’s website. Leave a few millimeters of space on each side to avoid rubbing when the tyre is wet or muddy.
Common Mistakes
- Buying by width alone and ignoring the bead seat diameter.
- Mixing inch and ETRTO sizes without converting them first.
- Assuming a tyre that fits one bike will fit another with the same wheel size.
- Forgetting that tyre width is measured on the rim, not just the sidewall label.
- Overinflating a wide tyre beyond the recommended pressure on the sidewall.
Recommended gear
A simple tread-depth gauge helps you judge when a tyre needs replacing, and a digital caliper makes measuring width and diameter accurate. A tyre lever set keeps you from pinching the tube when you remove and refit a tyre.
- Digital caliper for measuring tyre width and rim diameter. View on Amazon
- Tyre levers for removing and refitting bike tyres without damaging the tube. View on Amazon
- Tread depth gauge for checking when a bike tyre is worn out. View on Amazon
FAQ
What does the number on a bike tyre mean?
The first number in an ETRTO code is the tyre width in millimeters, and the second is the bead seat diameter. Inch sizes list the overall outer diameter and width in inches.
Can I use a wider tyre than the one on my bike?
Often yes, as long as the rim accepts that width and the frame or fork has enough clearance. Check both the rim’s recommended range and the frame’s maximum tyre size before buying.
How do I know if my tyre is the right size?
Match the bead seat diameter to your wheel size exactly, then choose a width your rim and frame support. If you are unsure, a local bike shop can confirm the fit.
Conclusion
Reading a bike tyre size chart comes down to three things: the bead seat diameter, the width, and the clearance on your frame. Confirm the diameter first, then choose a width that suits how you ride. When in doubt, measure your current tyre or check with a bike shop before ordering.
Ready to choose one?
About Caleb Morgan
Caleb Morgan is part of our editorial team and reviews and edits our cycling for beginners guides, checking product details against manufacturer specifications and owner feedback.
