Home305/70R18 vs 35x12.50R18

305/70R18 vs 35x12.50R18

The 35x12.50R18 is 35.00 in tall: 0.19 in (0.5%) taller than the 305/70R18 at 34.81 in. At an indicated 60 mph you'd be doing 60.3 mph.The 35x12.50R18 is 889.0 mm tall: 4.8 mm (0.5%) taller than the 305/70R18 at 884.2 mm. At an indicated 100 km/h you'd be doing 100.5 km/h.

By David Owen. Published 3 November 2026.

in, mphmm, km/h

Each figure is rounded separately, so related figures can differ in the last digit.

These are size-code figures only. Whether a size fits, clears and carries your load depends on your vehicle and the tire, so check with a tire shop.

What changes

The 35x12.50R18 is a flotation size: its 35.00 in height and 12.50 in width are the nominal numbers in the size code. The 305/70R18 is metric, 305 mm wide with each sidewall 70% of that, which works out at 34.81 in tall and 12.01 in wide. On paper the 35x12.50R18 is 0.19 in taller and 0.49 in wider.

Flotation sizes state their height and width in inches, and those numbers are nominal: makers aim at them, and real tires of the same size measure a little differently.

Makers' own measured diameters run 34.80 to 35.28 in for the 305/70R18 and 34.5 to 35.04 in for the 35x12.50R18, against the calculated 34.81 in and 35.00 in. Real tires vary by brand and tread design; the figures in the table come from the size code alone.

Speedometer and odometer

A speedometer that read true on the 305/70R18 reads low on the 35x12.50R18: an indicated 60 mph is a true 60.3 mph.A speedometer that read true on the 305/70R18 reads low on the 35x12.50R18: an indicated 100 km/h is a true 100.5 km/h.

The odometer records about 9,950 miles for every 10,000 you drive.The odometer records about 9,950 km for every 10,000 you drive.

Ground clearance and size class

Ground clearance at the axle rises by 0.09 in: half the diameter change, unloaded.Ground clearance at the axle rises by 2.4 mm: half the diameter change, unloaded. By calculated diameter both are 35-inch tires.

See every 35-inch size in metric.

Compare other sizes in the calculator