225/40R18 tire size
A 225/40R18 tire is 225 mm wide with a sidewall 40% of its width (90.0 mm), fits a 18-inch rim and has an overall diameter of 637 mm (25.1 in).
| Dimension | Metric | Imperial |
|---|---|---|
| Section width | 225 mm | 8.86 in |
| Sidewall height | 90.0 mm | 3.54 in |
| Rim diameter | 457.2 mm | 18 in |
| Overall diameter | 637.2 mm | 25.09 in |
| Circumference | 2,001.8 mm | 78.81 in |
| Revolutions | 500 per km | 804 per mile |
Reading the size 225/40R18
225Width in mm40Aspect ratio (sidewall % of width)RRadial construction18Rim diameter in inches
The load index and speed rating (for example 91V) follow the size on the sidewall. Replacement tires should match or exceed the original load index and speed rating.
Alternative sizes within 3% of 225/40R18
A replacement size should stay within about 3% of the original diameter so the speedometer, ABS and transmission stay accurate. Always check clearance, load index and the vehicle manufacturer's approved sizes.
Compare 225/40R18 with any size →