315/70R18 tire size
315/70R18 is a metric size: 35.4" tall, 12.4" wide, on a 18" rim — about a 35.5x12.50R18. The sidewall is 8.7" and the tire turns 570 times per mile.
315/70R18 specs
| Overall diameter (height) | 35.36" · 898 mm |
|---|---|
| Section width | 12.40" · 315 mm |
| Sidewall height | 8.68" · 220 mm (70% of width) |
| Rim diameter | 18" |
| Circumference | 111.09" · 2.822 m |
| Revolutions per mile | 570 (354 per km) |
| Inch (flotation) equivalent | 35.5x12.50R18 |
Equivalent sizes on a 18" rim
Sizes within ±5% of the overall diameter. Green rows are inside the usual ±3% limit for keeping the speedometer, ABS and gearing right; red rows are bigger changes that need clearance checks.
| Size | Diameter | Difference | Width | Speedo at 60 | |
|---|---|---|---|---|---|
| 35x12.50R18 common | 35.00" | -1.02% | +3 mm | 59.4 mph | calculate → |
| 295/70R18 common | 34.26" | -3.12% | -20 mm | 58.1 mph | calculate → |
| 285/75R18 | 34.83" | -1.50% | -30 mm | 59.1 mph | calculate → |
| 325/65R18 | 34.63" | -2.06% | +10 mm | 58.8 mph | calculate → |
| 305/70R18 | 34.81" | -1.56% | -10 mm | 59.1 mph | calculate → |
| 37x13.50R18 | 37.00" | +4.63% | +28 mm | 62.8 mph | calculate → |
| 305/65R18 | 33.61" | -4.95% | -10 mm | 57.0 mph | calculate → |
| 37x12.50R18 | 37.00" | +4.63% | +3 mm | 62.8 mph | calculate → |
| 285/70R18 | 33.71" | -4.68% | -30 mm | 57.2 mph | calculate → |
| 35x11.50R18 | 35.00" | -1.02% | -23 mm | 59.4 mph | calculate → |
| 35x13.00R18 | 35.00" | -1.02% | +15 mm | 59.4 mph | calculate → |
| 35x14.50R18 | 35.00" | -1.02% | +53 mm | 59.4 mph | calculate → |
| 36x13.50R18 | 36.00" | +1.80% | +28 mm | 61.1 mph | calculate → |
| 34x12.50R18 | 34.00" | -3.85% | +3 mm | 57.7 mph | calculate → |
| 37x11.50R18 | 37.00" | +4.63% | -23 mm | 62.8 mph | calculate → |
| 35x13.50R18 | 35.00" | -1.02% | +28 mm | 59.4 mph | calculate → |
| 355/65R18 | 36.17" | +2.28% | +40 mm | 61.4 mph | calculate → |
| 37x14.50R18 | 37.00" | +4.63% | +53 mm | 62.8 mph | calculate → |
Try another size against 315/70R18
Questions
What size is 315/70R18 in inches?
315/70R18 is about 35.4" tall and 12.4" wide on a 18-inch rim — roughly a 35.5x12.50R18 in inch sizing.
What does 315/70R18 mean?
315 mm section width, sidewall 70% of the width (8.68"), radial construction, 18-inch rim.
What tire sizes are equivalent to 315/70R18?
On the same 18" rim, within 3% of the diameter: 35x11.50R18 (-1.02%), 35x12.50R18 (-1.02%), 35x13.50R18 (-1.02%), 35x13.00R18 (-1.02%), 35x14.50R18 (-1.02%), 285/75R18 (-1.50%).
How many revolutions per mile does a 315/70R18 tire make?
About 570 revolutions per mile (circumference 111.1").
How these numbers are computed
Diameter = rim + 2 × sidewall, sidewall = width × aspect ÷ 100, circumference = π × diameter, revolutions per mile = 63,360 ÷ circumference. Real tires differ by brand by a few tenths of an inch. Last reviewed October 14, 2026.