Tire Ruler225/55R18 dimensions
| Overall diameter (height) | 27.74″ · 705 mm |
| Section width | 8.86″ · 225 mm |
| Sidewall height | 4.87″ · 124 mm |
| Wheel diameter | 18″ |
| Rim width (rule of thumb) | 6–8″ |
| Circumference | 87.2″ |
| Revolutions per mile | 727 |
| In inches (flotation style) | 27.7 × 8.9R18 |
How it’s calculated: the sidewall is 55% of the 225 mm width = 123.8 mm (4.87″). Add two sidewalls to the 18″ wheel: 18 + 2 × 4.87 = 27.74″.
Bigger tires than 225/55R18 on 18″ wheels
| Size | Height | Taller by | 60 mph reads |
|---|---|---|---|
| 235/55R18 | 28.2″ | +0.43″ (+1.6%) | 60.9 mph |
| 225/60R18 | 28.6″ | +0.89″ (+3.2%) | 61.9 mph |
| 255/55R18 | 29.0″ | +1.30″ (+4.7%) | 62.8 mph |
| 235/60R18 | 29.1″ | +1.36″ (+4.9%) | 62.9 mph |
| 245/60R18 | 29.6″ | +1.83″ (+6.6%) | 64.0 mph |
“60 mph reads” is your real speed when a speedometer set up for 225/55R18 shows 60. Above about 3% taller, most trucks need a leveling kit or lift, and the speedometer should be recalibrated.
Same height on a different wheel size
Changing wheel size (plus or minus sizing) while keeping the overall height keeps your speedometer right:
- 225/70R15: 27.4″ tall on a 15″ wheel (−1.2%)
- 215/70R16: 27.9″ tall on a 16″ wheel (+0.4%)
- 235/60R17: 28.1″ tall on a 17″ wheel (+1.3%)
- 225/60R17: 27.6″ tall on a 17″ wheel (−0.4%)
- 245/45R19: 27.7″ tall on a 19″ wheel (−0.2%)
Frequently asked questions
Is 225/55R18 a 28 inch tire?
Not quite. 225/55R18 is 27.74 inches tall, between a 27 and a 28 inch tire.
What size is 225/55R18 in inches?
225/55R18 is 27.7 inches tall (overall diameter), 8.9 inches wide, with a 4.9 inch sidewall, and fits an 18 inch wheel.
What tire size is equivalent to 225/55R18?
No common size on an 18" wheel is within 1.5% of 225/55R18's diameter. Use the calculator above to compare any size.
What rim width fits 225/55R18?
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 225/55R18 make?
About 727 revolutions per mile in theory (circumference 87.2 in). Real tires turn slightly more because they flatten under load.