225/55R18 tire size
A 225/55R18 tire is 27.7 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
- 27.74″ (705 mm)
- Section width
- 8.86″ (225 mm)
- Sidewall height
- 4.87″ (124 mm)
- Wheel diameter
- 18″
- Circumference
- 87.2″
- Revolutions per mile
- 727
What 225/55R18 means
- 225: the tire is 225 mm (8.9 in) wide from sidewall to sidewall.
- 55: the sidewall is 55% of the width, 123.8 mm (4.87 in) tall.
- R: radial construction, used by almost every modern tire.
- 18: it fits a 18-inch wheel.
Overall diameter = 18 + 2 × 4.87 = 27.74 inches.
Sizes equivalent to 225/55R18
These sizes are within 3% of the overall diameter, the usual limit for swapping without speedometer problems.
| Size | Diameter | Difference | Speedometer at 60 mph |
|---|---|---|---|
| 245/40R20 | 27.7″ | -0.1% | 59.9 mph actual |
| 205/60R18 | 27.7″ | -0.2% | 59.9 mph actual |
| 245/45R19 | 27.7″ | -0.2% | 59.9 mph actual |
| 245/50R18 | 27.6″ | -0.4% | 59.8 mph actual |
| 225/50R19 | 27.9″ | +0.4% | 60.2 mph actual |
| 215/45R20 | 27.6″ | -0.5% | 59.7 mph actual |
| 205/55R19 | 27.9″ | +0.5% | 60.3 mph actual |
| 225/45R20 | 28.0″ | +0.8% | 60.5 mph actual |
| 215/50R19 | 27.5″ | -1.0% | 59.4 mph actual |
| 205/50R20 | 28.1″ | +1.2% | 60.7 mph actual |
Going a size taller? 235/55R18 is 28.2″ tall, 1.6% more than 225/55R18. Compare any two sizes in the tire size calculator.
See every common size side by side in the tire size chart.
Questions
What is 225/55R18 in inches?
A 225/55R18 tire is about 27.7 inches tall (705 mm) and 8.9 inches wide, on a 18-inch wheel. In flotation sizing that's roughly 27.7x8.9R18.
How tall is a 225/55R18 tire?
The overall diameter is 27.74 inches: the 18-inch wheel plus two 4.87-inch sidewalls. Actual tires vary by a few tenths of an inch between brands and models.
Can I put 235/55R18 instead of 225/55R18?
235/55R18 is 0.43 inches taller (1.6%) 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 225/55R18 make?
About 727 revolutions per mile, from a circumference of 87.2 inches.
