315/40R18 tire size in inches
A 315/40R18 tire measures
27.9" tall × 12.4" wide
4.96" sidewall on a 18" wheel. 722 revolutions per mile.
315/40R18 means a tire 315 mm wide, with sidewalls 40% as tall as the tire is wide (126 mm), radial construction (R), for a 18 inch wheel.
315/40R18 specs
| Overall diameter (height) | 27.92 inches (709 mm) |
|---|---|
| Section width | 12.40 inches (315 mm) |
| Sidewall height | 4.96 inches (126 mm) |
| Wheel (rim) diameter | 18 inches |
| Circumference | 87.7 inches (2,228 mm) |
| Revolutions per mile | 722 |
| Revolutions per kilometer | 449 |
| Approximate rim width | 10.5" to 12.0" |
| In inches (flotation style) | 27.9x12.4R18 |
| 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 315/40R18 on a 18" wheel
These 18" sizes are within 3% of 315/40R18's overall diameter, the range most tire shops treat as interchangeable.
| Size | Diameter | Width | Difference | Real speed at 60 | |
|---|---|---|---|---|---|
| 195/65R18 | 27.98" | 7.68" | +0.2% | 60.1 mph | Compare |
| 255/50R18 | 28.04" | 10.04" | +0.4% | 60.3 mph | Compare |
| 225/55R18 | 27.74" | 8.86" | −0.6% | 59.6 mph | Compare |
| 275/45R18 | 27.74" | 10.83" | −0.6% | 59.6 mph | Compare |
| 285/45R18 | 28.10" | 11.22" | +0.6% | 60.4 mph | Compare |
| 205/60R18 | 27.69" | 8.07" | −0.8% | 59.5 mph | Compare |
| 215/60R18 | 28.16" | 8.46" | +0.8% | 60.5 mph | Compare |
| 235/55R18 | 28.18" | 9.25" | +0.9% | 60.5 mph | Compare |
| 245/50R18 | 27.65" | 9.65" | −1.0% | 59.4 mph | Compare |
| 305/40R18 | 27.61" | 12.01" | −1.1% | 59.3 mph | Compare |
| 325/40R18 | 28.24" | 12.80" | +1.1% | 60.7 mph | Compare |
| 265/50R18 | 28.43" | 10.43" | +1.8% | 61.1 mph | Compare |
Same height on other wheel sizes (plus and minus sizing)
| Size | Wheel | Diameter | Difference | |
|---|---|---|---|---|
| 185/75R17 | 17" | 27.93" | 0.0% | Compare |
| 205/80R15 | 15" | 27.91" | 0.0% | Compare |
| 335/30R20 | 20" | 27.91" | 0.0% | Compare |
| 275/55R16 | 16" | 27.91" | 0.0% | Compare |
| 235/70R15 | 15" | 27.95" | +0.1% | Compare |
| 325/35R19 | 19" | 27.96" | +0.1% | Compare |
| 205/55R19 | 19" | 27.88" | −0.2% | Compare |
| 235/75R14 | 14" | 27.88" | −0.2% | Compare |
| 295/30R21 | 21" | 27.97" | +0.2% | Compare |
| 225/45R20 | 20" | 27.97" | +0.2% | Compare |
| 285/40R19 | 19" | 27.98" | +0.2% | Compare |
| 225/50R19 | 19" | 27.86" | −0.2% | Compare |
One size up or down
- 305/40R18narrower: 27.6" × 12.0"
- 325/40R18wider: 28.2" × 12.8"
- 315/35R18lower profile: 26.7" × 12.4"
- 315/45R18taller sidewall: 29.2" × 12.4"
Compare 315/40R18 with another size
Questions
- How tall is a 315/40R18 tire?
- A 315/40R18 tire is 27.9 inches tall (709 mm), calculated from the size. It is 12.4 inches wide with 5.0 inches sidewalls. Real tires vary by a few tenths of an inch between brands and tread patterns.
- What does 315/40R18 mean?
- 315/40R18 means a tire 315 mm wide, with sidewalls 40% as tall as the tire is wide (126 mm), radial construction (R), for a 18 inch wheel.
- How many revolutions per mile does a 315/40R18 tire make?
- About 722 revolutions per mile, based on a circumference of 87.7 inches. Under load the tire flattens slightly, so the maker's published figure is usually a little higher.
- What rim width fits a 315/40R18 tire?
- Roughly 10.5" to 12.0". Check the tire maker's approved rim range for the exact model before buying wheels.
- Can I use 195/65R18 instead of 315/40R18?
- 195/65R18 is +0.06 inches (+0.2%) in overall diameter, so at an indicated 60 mph you would be doing 60.1 mph. Differences under 3% are usually fine, but check clearance, load index and your vehicle's placard.