Tire Ruler225/45R18 dimensions
| Overall diameter (height) | 25.97″ · 660 mm |
| Section width | 8.86″ · 225 mm |
| Sidewall height | 3.99″ · 101 mm |
| Wheel diameter | 18″ |
| Rim width (rule of thumb) | 6–8″ |
| Circumference | 81.6″ |
| Revolutions per mile | 777 |
| In inches (flotation style) | 26.0 × 8.9R18 |
How it’s calculated: the sidewall is 45% of the 225 mm width = 101.3 mm (3.99″). Add two sidewalls to the 18″ wheel: 18 + 2 × 3.99 = 25.97″.
Bigger tires than 225/45R18 on 18″ wheels
| Size | Height | Taller by | 60 mph reads |
|---|---|---|---|
| 235/45R18 | 26.3″ | +0.35″ (+1.4%) | 60.8 mph |
| 245/45R18 | 26.7″ | +0.71″ (+2.7%) | 61.6 mph |
| 235/50R18 | 27.3″ | +1.28″ (+4.9%) | 63.0 mph |
| 215/55R18 | 27.3″ | +1.34″ (+5.2%) | 63.1 mph |
| 225/55R18 | 27.7″ | +1.77″ (+6.8%) | 64.1 mph |
“60 mph reads” is your real speed when a speedometer set up for 225/45R18 shows 60. Above about 3% taller, most trucks need a leveling kit or lift, and the speedometer should be recalibrated.
Sizes equivalent to 225/45R18
Within 1.5% of the same height on an 18″ wheel. Usually interchangeable for the speedometer; check width, load index and clearance.
| Size | Height | Width | Difference |
|---|---|---|---|
| 245/40R18 | 25.7″ | 9.6″ | −1.0% |
| 235/45R18 | 26.3″ | 9.3″ | +1.4% |
Same height on a different wheel size
Changing wheel size (plus or minus sizing) while keeping the overall height keeps your speedometer right:
- 205/70R15: 26.3″ tall on a 15″ wheel (+1.3%)
- 205/60R16: 25.7″ tall on a 16″ wheel (−1.1%)
- 215/60R16: 26.2″ tall on a 16″ wheel (+0.7%)
- 215/55R17: 26.3″ tall on a 17″ wheel (+1.3%)
- 225/50R17: 25.9″ tall on a 17″ wheel (−0.4%)
Frequently asked questions
Is 225/45R18 a 26 inch tire?
Yes. 225/45R18 is 25.97 inches tall, so it's sold and talked about as a 26-inch tire.
What size is 225/45R18 in inches?
225/45R18 is 26.0 inches tall (overall diameter), 8.9 inches wide, with a 4.0 inch sidewall, and fits an 18 inch wheel.
What tire size is equivalent to 225/45R18?
Sizes within 1.5% of the same diameter on an 18" wheel: 245/40R18 (25.7"), 235/45R18 (26.3"). Check load index and width before swapping.
What rim width fits 225/45R18?
As a rule of thumb, about 6–8 inches. The tire maker's spec sheet lists the approved range for each model.
How many revolutions per mile does 225/45R18 make?
About 777 revolutions per mile in theory (circumference 81.6 in). Real tires turn slightly more because they flatten under load.