225/40R18 Tire Size
Dimensions of a 225/40R18 tire in inches and millimeters, with equivalent and plus sizes.
225/40R18 dimensions
A 225/40R18 tire is 225 mm wide with a sidewall that is 40% of the width (90 mm), mounted on a 18-inch rim. Its overall diameter is about 25.09 inches (637 mm), so it is roughly a 25.1-inch tall tire.
| Overall diameter | 25.09 in | 637 mm |
|---|---|---|
| Section width | 8.86 in | 225 mm |
| Sidewall height | 3.54 in | 90.0 mm |
| Rim diameter | 18 in | 457 mm |
| Circumference | 78.8 in | 2002 mm |
| Revolutions | 804 per mile | 500 per km |
Equivalent sizes on a 18-inch rim
These sizes stay within ±3% of the 225/40R18 diameter on the same rim — the range most tire shops use. Not every size is made in every tire model, and only sizes approved for your vehicle (with the right load and speed rating) should be fitted.
| Size | Diameter | mm | Difference |
|---|---|---|---|
| 205/45R18 | 25.26 in | 642 mm | +0.7% |
| 235/40R18 | 25.40 in | 645 mm | +1.3% |
| 215/40R18 | 24.77 in | 629 mm | -1.3% |
| 245/35R18 | 24.75 in | 629 mm | -1.3% |
| 215/45R18 | 25.62 in | 651 mm | +2.1% |
| 235/35R18 | 24.48 in | 622 mm | -2.4% |
| 205/40R18 | 24.46 in | 621 mm | -2.5% |
| 245/40R18 | 25.72 in | 653 mm | +2.5% |
Plus and minus sizes
Changing the rim size? These options on 17-, 19- and 20-inch rims keep the overall diameter within ±3%.
| Size | Diameter | mm | Difference |
|---|---|---|---|
| 215/30R20 | 25.08 in | 637 mm | -0.0% |
| 255/40R17 | 25.03 in | 636 mm | -0.2% |
| 255/30R19 | 25.02 in | 636 mm | -0.3% |
| 255/25R20 | 25.02 in | 636 mm | -0.3% |
| 225/35R19 | 25.20 in | 640 mm | +0.5% |
| 225/45R17 | 24.97 in | 634 mm | -0.5% |
| 215/35R19 | 24.93 in | 633 mm | -0.6% |
| 225/30R20 | 25.31 in | 643 mm | +0.9% |
| 235/45R17 | 25.33 in | 643 mm | +1.0% |
| 245/25R20 | 24.82 in | 630 mm | -1.1% |
Compare 225/40R18 with another size →
Frequently asked questions
How tall is a 225/40R18 tire?
About 25.09 inches (637 mm) in overall diameter.
How wide is a 225/40R18 tire?
The section width is 225 mm, about 8.9 inches.
What size can replace 225/40R18?
On the same rim, 205/45R18 is the closest size (+0.7% diameter). Use only sizes approved for your vehicle.
How many revolutions per mile does a 225/40R18 tire make?
About 804 revolutions per mile (500 per km).
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