225/65R16 vs 245/50R18

245/50R18 is 0.13 in (3.3 mm) taller than 225/65R16, a +0.47% diameter difference. With the speedometer set for 225/65R16, an indicated 60 mph is 60.3 mph on 245/50R18.

Is this a safe swap?

Diameter difference +0.47%: under 1%

By overall diameter alone, 245/50R18 is a near match for 225/65R16; the speedometer changes by less than 1%. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

Side profile and tread width, drawn to the same scale.

225/65R16 vs 245/50R18 differences
Measurement	225/65R16	245/50R18	Difference	% diff
Overall diameter	27.52 in (698.9 mm)	27.65 in (702.2 mm)	+0.13 in (+3.3 mm)	+0.47%
Sidewall height	5.76 in (146.3 mm)	4.82 in (122.5 mm)	−0.94 in (−23.7 mm)	−16.24%
Section width	8.86 in (225.0 mm)	9.65 in (245.0 mm)	+0.79 in (+20.0 mm)	+8.89%
Circumference	86.44 in (2,195.7 mm)	86.85 in (2,206.0 mm)	+0.41 in (+10.4 mm)	+0.47%
Revolutions per mile	733	730	−3	−0.47%

True speed with the speedometer calibrated for 225/65R16
Indicated	Actual on 225/65R16	Actual on 245/50R18	Difference
30 mph	30.0 mph	30.1 mph	+0.1 mph
60 mph	60.0 mph	60.3 mph	+0.3 mph
75 mph	75.0 mph	75.4 mph	+0.4 mph

Ride-height change: 245/50R18 raises the vehicle by 0.06 in (1.7 mm) at the axle (half the +3.3 mm diameter difference).

245/50R18 is 0.13 in taller than 225/65R16 and 20 mm wider, a 0.47% difference in overall diameter.

With the speedometer calibrated for 225/65R16, an indicated 60 mph is actually 60.3 mph on 245/50R18, and revolutions per mile change from 733 to 730.

245/50R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 225/65R16.

Size pages

Other comparisons with 225/65R16

Other comparisons with 245/50R18

Source: Calculated from standard tire geometry formulas. Verified 2026-09-27. How these numbers are calculated.