Bicycle Tire Size Chart
Look up bicycle tire sizes with ISO/ETRTO codes, diameter, and rolling circumference for cycle-computer setup.
By Jonas Lindemann · Updated · How we build our calculators
2105mm circumference
ISO/ETRTO 25-622 · use this value for cycle-computer setup
82.9 in
Circumference
670 mm
Diameter
26.4 in
Diameter
Bicycle Tire Size Reference Chart
| Common Size | ISO / ETRTO | Category | Circumference |
|---|---|---|---|
| 700 x 23c | 23-622 | Road 700c | 2096 mm |
| 700 x 25c | 25-622 | Road 700c | 2105 mm |
| 700 x 28c | 28-622 | Road 700c | 2136 mm |
| 700 x 32c | 32-622 | Gravel 700c | 2155 mm |
| 700 x 38c | 38-622 | Gravel 700c | 2180 mm |
| 29 x 2.1 (29er) | 54-622 | MTB 29" | 2288 mm |
| 27.5 x 2.1 (650b) | 54-584 | MTB 27.5" | 2148 mm |
| 26 x 1.95 | 50-559 | MTB 26" | 2050 mm |
| 26 x 2.1 | 54-559 | MTB 26" | 2068 mm |
| 24 x 1.75 | 47-507 | Junior / cruiser | 1888 mm |
| 20 x 1.75 (BMX) | 47-406 | BMX 20" | 1515 mm |
| 16 x 1.75 | 47-305 | Kids 16" | 1206 mm |
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Calculation Method
Bicycle Tire Size Chart: Decode Every Marking
Bicycle tire sizes can look confusing because the same tire may carry several different labels. This chart maps common sizes to the ISO/ETRTO standard and gives the diameter and rolling circumference you need.
The ISO / ETRTO Standard
ISO sizing is the only system that always matches. A code like 25-622 means a 25 mm wide tire on a 622 mm (700c) rim. The second number is the bead-seat diameter and must match your rim, so two tires share a rim if their second ISO number is the same.
Circumference for Your Cycle Computer
Bike computers and GPS units need your tire's rolling circumference to report speed and distance accurately. A 700x25c is about 2105 mm, a 700x28c about 2136 mm, and a 29-inch MTB tire about 2288 mm. For the best accuracy you can measure your own roll-out, since width, pressure, and load all shift the value slightly.
Common Categories
Road and gravel tires use 700c (ISO 622) rims; modern mountain bikes use 29-inch (622), 27.5-inch (584), or 26-inch (559); BMX uses 20-inch (406). The reference table lists each with its ISO code and circumference.
Frequently Asked Questions
Tires usually show a common size like 700x25c or 26x2.1, plus an ISO/ETRTO code like 25-622. The ISO code is the most reliable: the first number is the tire width in millimeters and the second is the bead-seat (rim) diameter, which must match your rim.
Use the rolling circumference for your exact tire size. A 700x25c is about 2105 mm, a 700x28c about 2136 mm, and a 29-inch MTB tire about 2288 mm. For best accuracy you can measure your own roll-out, since pressure and load change it slightly.
Yes. 700x28c means a tire roughly 28 mm wide on a 700c (ISO 622) rim, written 28-622 in ISO form. The c is an old French width code, not a separate measurement.