225/45R18 tire size
A 225/45R18 tire is 26.0 inches tall and 8.9 inches wide. Here are its full dimensions, what the numbers mean, and the sizes you can swap it for.
- Overall diameter
- 25.97″ (660 mm)
- Section width
- 8.86″ (225 mm)
- Sidewall height
- 3.99″ (101 mm)
- Wheel diameter
- 18″
- Circumference
- 81.6″
- Revolutions per mile
- 777
What 225/45R18 means
- 225: the tire is 225 mm (8.9 in) wide from sidewall to sidewall.
- 45: the sidewall is 45% of the width, 101.3 mm (3.99 in) tall.
- R: radial construction, used by almost every modern tire.
- 18: it fits a 18-inch wheel.
Overall diameter = 18 + 2 × 3.99 = 25.97 inches.
Sizes equivalent to 225/45R18
These sizes are within 3% of the overall diameter, the usual limit for swapping without speedometer problems.
| Size | Diameter | Difference | Speedometer at 60 mph |
|---|---|---|---|
| 215/35R20 | 25.9″ | -0.2% | 59.9 mph actual |
| 205/50R18 | 26.1″ | +0.4% | 60.2 mph actual |
| 225/40R19 | 26.1″ | +0.4% | 60.3 mph actual |
| 215/40R19 | 25.8″ | -0.8% | 59.5 mph actual |
| 245/35R19 | 25.8″ | -0.8% | 59.5 mph actual |
| 225/35R20 | 26.2″ | +0.9% | 60.5 mph actual |
| 245/40R18 | 25.7″ | -1.0% | 59.4 mph actual |
| 205/45R19 | 26.3″ | +1.1% | 60.7 mph actual |
| 205/35R20 | 25.6″ | -1.2% | 59.3 mph actual |
| 215/45R18 | 25.6″ | -1.4% | 59.2 mph actual |
Going a size taller? 235/45R18 is 26.3″ tall, 1.4% more than 225/45R18. Compare any two sizes in the tire size calculator.
See every common size side by side in the tire size chart.
Questions
What is 225/45R18 in inches?
A 225/45R18 tire is about 26.0 inches tall (660 mm) and 8.9 inches wide, on a 18-inch wheel. In flotation sizing that's roughly 26.0x8.9R18.
How tall is a 225/45R18 tire?
The overall diameter is 25.97 inches: the 18-inch wheel plus two 3.99-inch sidewalls. Actual tires vary by a few tenths of an inch between brands and models.
Can I put 235/45R18 instead of 225/45R18?
235/45R18 is 0.35 inches taller (1.4%) and 10 mm wider. That's within the usual 3% limit, but check that your wheel width is approved for it and that it clears the suspension.
How many revolutions per mile does a 225/45R18 make?
About 777 revolutions per mile, from a circumference of 81.6 inches.
