Quick chart: common bike tire sizes
The bead seat diameter (BSD) is the number that has to match your rim. Names differ between road, mountain and older bikes, but the BSD is the same wherever the sizes are interchangeable.
| Common name | ETRTO bead seat diameter | Typically found on |
|---|---|---|
| 12 inch | 203 mm | Small kids’ bikes |
| 16 inch | 305 mm | Kids’ bikes |
| 18 inch | 355 mm | Kids’ bikes |
| 20 inch (BMX) | 406 mm | BMX, kids’ bikes |
| 24 inch | 507 mm | Older kids’ bikes |
| 26 inch (mountain) | 559 mm | Older mountain bikes, fat bikes, cruisers |
| 650b / 27.5 inch | 584 mm | Mountain, gravel, touring |
| 700c / 29 inch | 622 mm | Road, hybrid, gravel, 29er mountain |
Sizes are listed in a rough order of rim diameter. For a wheel-focused view, see the bike wheel size chart. Treat the chart as a starting point and confirm with the numbers on your tire sidewall.
Less common and older sizes
A few older sizes look similar to the ones above but are not interchangeable:
| Label | ETRTO bead seat diameter |
|---|---|
| 27 inch (27 x 1 1/4) | 630 mm |
| 700B / 28 x 1 1/2 | 635 mm |
| 26 x 1 3/8 | 590 mm |
| 650c | 571 mm |
| 20 x 1 3/8 | 451 mm |
A 27 inch tire does not fit a 700c rim and vice versa. See what 700c really means for that common mix-up.
Typical tire widths by bike type
These ranges are general; your frame, fork and rim set the real limits.
- Road: roughly 25 to 32 mm
- Hybrid and commuter: roughly 28 to 45 mm
- Gravel: roughly 35 to 50 mm
- Mountain: roughly 2.1 to 2.6 inches
- Fat bike: roughly 3.8 to 5 inches
Always check your frame manufacturer’s maximum tire clearance.
How to read 700x28c
Marking 700x28c is French metric: 700 is the approximate outside diameter in millimeters, 28 is the width in millimeters, and c is a legacy letter associated with the 622 mm rim. If you also see 28-622 on the sidewall, that is the same tire described in ETRTO, and it is the number to trust. For all three systems, see bike tire sizes explained.
Rim width and tire width
Each rim has a recommended range of tire widths. A tire that is far too narrow or wide for the rim can be hard to mount and may handle poorly. To see the inside width of a rim, look for markings or specifications from the rim maker, or measure the inner width between the rim hooks with a caliper once the tire is off. Measuring a rim with the tire still mounted is unreliable.
Using the chart
- Read the ETRTO number on your current tire.
- Find the matching BSD in the chart.
- Choose a width that suits your riding and fits your frame.
If the sidewall is worn off, follow how to find and measure your bike tire size. To translate inches into millimeters, use converting between inch, metric and ETRTO sizes.