225/40R18 tire size in inches
A 225/40R18 tire measures
25.1" tall × 8.9" wide
3.54" sidewall on a 18" wheel. 804 revolutions per mile.
225/40R18 means a tire 225 mm wide, with sidewalls 40% as tall as the tire is wide (90 mm), radial construction (R), for a 18 inch wheel.
225/40R18 specs
| Overall diameter (height) | 25.09 inches (637 mm) |
|---|---|
| Section width | 8.86 inches (225 mm) |
| Sidewall height | 3.54 inches (90 mm) |
| Wheel (rim) diameter | 18 inches |
| Circumference | 78.8 inches (2,002 mm) |
| Revolutions per mile | 804 |
| Revolutions per kilometer | 500 |
| Approximate rim width | 7.5" to 9.0" |
| In inches (flotation style) | 25.1x8.9R18 |
| Aspect ratio | 40% |
Calculated from the size. Real tires differ by brand, model and tread depth, typically by a few tenths of an inch.
Sizes that can replace 225/40R18 on a 18" wheel
These 18" sizes are within 3% of 225/40R18's overall diameter, the range most tire shops treat as interchangeable.
| Size | Diameter | Width | Difference | Real speed at 60 | |
|---|---|---|---|---|---|
| 255/35R18 | 25.03" | 10.04" | −0.2% | 59.9 mph | Compare |
| 205/45R18 | 25.26" | 8.07" | +0.7% | 60.4 mph | Compare |
| 195/45R18 | 24.91" | 7.68" | −0.7% | 59.6 mph | Compare |
| 265/35R18 | 25.30" | 10.43" | +0.9% | 60.5 mph | Compare |
| 215/40R18 | 24.77" | 8.46" | −1.3% | 59.2 mph | Compare |
| 235/40R18 | 25.40" | 9.25" | +1.3% | 60.8 mph | Compare |
| 245/35R18 | 24.75" | 9.65" | −1.3% | 59.2 mph | Compare |
| 275/35R18 | 25.58" | 10.83" | +2.0% | 61.2 mph | Compare |
| 215/45R18 | 25.62" | 8.46" | +2.1% | 61.3 mph | Compare |
| 195/50R18 | 25.68" | 7.68" | +2.4% | 61.4 mph | Compare |
| 235/35R18 | 24.48" | 9.25" | −2.4% | 58.5 mph | Compare |
| 245/40R18 | 25.72" | 9.65" | +2.5% | 61.5 mph | Compare |
Same height on other wheel sizes (plus and minus sizing)
| Size | Wheel | Diameter | Difference | |
|---|---|---|---|---|
| 215/30R20 | 20" | 25.08" | 0.0% | Compare |
| 285/45R15 | 15" | 25.10" | 0.0% | Compare |
| 235/60R14 | 14" | 25.10" | +0.1% | Compare |
| 205/50R17 | 17" | 25.07" | −0.1% | Compare |
| 205/75R13 | 13" | 25.11" | +0.1% | Compare |
| 295/35R17 | 17" | 25.13" | +0.2% | Compare |
| 165/85R14 | 14" | 25.04" | −0.2% | Compare |
| 255/55R14 | 14" | 25.04" | −0.2% | Compare |
| 255/50R15 | 15" | 25.04" | −0.2% | Compare |
| 255/45R16 | 16" | 25.04" | −0.2% | Compare |
| 255/40R17 | 17" | 25.03" | −0.2% | Compare |
| 235/65R13 | 13" | 25.03" | −0.2% | Compare |
One size up or down
- 215/40R18narrower: 24.8" × 8.5"
- 235/40R18wider: 25.4" × 9.3"
- 225/35R18lower profile: 24.2" × 8.9"
- 225/45R18taller sidewall: 26.0" × 8.9"
Compare 225/40R18 with another size
Questions
- How tall is a 225/40R18 tire?
- A 225/40R18 tire is 25.1 inches tall (637 mm), calculated from the size. It is 8.9 inches wide with 3.5 inches sidewalls. Real tires vary by a few tenths of an inch between brands and tread patterns.
- What does 225/40R18 mean?
- 225/40R18 means a tire 225 mm wide, with sidewalls 40% as tall as the tire is wide (90 mm), radial construction (R), for a 18 inch wheel.
- How many revolutions per mile does a 225/40R18 tire make?
- About 804 revolutions per mile, based on a circumference of 78.8 inches. Under load the tire flattens slightly, so the maker's published figure is usually a little higher.
- What rim width fits a 225/40R18 tire?
- Roughly 7.5" to 9.0". Check the tire maker's approved rim range for the exact model before buying wheels.
- Can I use 255/35R18 instead of 225/40R18?
- 255/35R18 is −0.06 inches (−0.2%) in overall diameter, so at an indicated 60 mph you would be doing 59.9 mph. Differences under 3% are usually fine, but check clearance, load index and your vehicle's placard.