305/70R18 tire size
305/70R18 is a metric size: 34.8" tall, 12.0" wide, on a 18" rim — about a 35x12.00R18. The sidewall is 8.4" and the tire turns 579 times per mile.
305/70R18 specs
| Overall diameter (height) | 34.81" · 884 mm |
|---|---|
| Section width | 12.01" · 305 mm |
| Sidewall height | 8.41" · 214 mm (70% of width) |
| Rim diameter | 18" |
| Circumference | 109.36" · 2.778 m |
| Revolutions per mile | 579 (360 per km) |
| Inch (flotation) equivalent | 35x12.00R18 |
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 | |
|---|---|---|---|---|---|
| 275/70R18 common | 33.16" | -4.75% | -30 mm | 57.1 mph | compare → |
| 35x12.50R18 common | 35.00" | +0.54% | +13 mm | 60.3 mph | compare → |
| 295/70R18 common | 34.26" | -1.58% | -10 mm | 59.0 mph | compare → |
| 285/75R18 | 34.83" | +0.06% | -20 mm | 60.0 mph | compare → |
| 325/65R18 | 34.63" | -0.51% | +20 mm | 59.7 mph | compare → |
| 305/65R18 | 33.61" | -3.45% | 0 mm | 57.9 mph | compare → |
| 285/70R18 | 33.71" | -3.17% | -20 mm | 58.1 mph | compare → |
| 325/60R18 | 33.35" | -4.18% | +20 mm | 57.5 mph | compare → |
| 35x11.50R18 | 35.00" | +0.54% | -13 mm | 60.3 mph | calculate → |
| 295/65R18 | 33.10" | -4.92% | -10 mm | 57.0 mph | calculate → |
| 315/70R18 | 35.36" | +1.58% | +10 mm | 61.0 mph | calculate → |
| 35x13.00R18 | 35.00" | +0.54% | +25 mm | 60.3 mph | calculate → |
| 35x14.50R18 | 35.00" | +0.54% | +63 mm | 60.3 mph | calculate → |
| 34x12.50R18 | 34.00" | -2.33% | +13 mm | 58.6 mph | calculate → |
| 36x13.50R18 | 36.00" | +3.42% | +38 mm | 62.0 mph | calculate → |
| 35x13.50R18 | 35.00" | +0.54% | +38 mm | 60.3 mph | calculate → |
| 355/65R18 | 36.17" | +3.90% | +50 mm | 62.3 mph | calculate → |
Plus / minus sizing: 17" and 19" rims
Same overall height on a different rim. Check wheel width and clearance before switching.
| Size | Diameter | Difference | Width | Speedo at 60 | |
|---|---|---|---|---|---|
| 35x12.50R17 common | 35.00" | +0.54% | +13 mm | 60.3 mph | compare → |
| 35x11.50R17 | 35.00" | +0.54% | -13 mm | 60.3 mph | calculate → |
| 35x14.50R17 | 35.00" | +0.54% | +63 mm | 60.3 mph | calculate → |
| 35x13.50R17 | 35.00" | +0.54% | +38 mm | 60.3 mph | calculate → |
| 35x10.50R17 | 35.00" | +0.54% | -38 mm | 60.3 mph | calculate → |
| 325/70R17 | 34.91" | +0.29% | +20 mm | 60.2 mph | calculate → |
Try another size against 305/70R18
Questions
What size is 305/70R18 in inches?
305/70R18 is about 34.8" tall and 12.0" wide on a 18-inch rim — roughly a 35x12.00R18 in inch sizing.
What does 305/70R18 mean?
305 mm section width, sidewall 70% of the width (8.41"), radial construction, 18-inch rim.
What tire sizes are equivalent to 305/70R18?
On the same 18" rim, within 3% of the diameter: 285/75R18 (+0.06%), 325/65R18 (-0.51%), 35x11.50R18 (+0.54%), 35x12.50R18 (+0.54%), 35x13.50R18 (+0.54%), 35x13.00R18 (+0.54%).
How many revolutions per mile does a 305/70R18 tire make?
About 579 revolutions per mile (circumference 109.4").
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.