215/65R16 vs 225/50R18

225/50R18 is 0.15 in (3.7 mm) shorter than 215/65R16, a −0.54% diameter difference. With the speedometer set for 215/65R16, an indicated 60 mph is 59.7 mph on 225/50R18.

Is this a safe swap?

Diameter difference −0.54%: under 1%

By overall diameter alone, 225/50R18 is a near match for 215/65R16; 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.

215/65R16 vs 225/50R18 differences
Measurement	215/65R16	225/50R18	Difference	% diff
Overall diameter	27.00 in (685.9 mm)	26.86 in (682.2 mm)	−0.15 in (−3.7 mm)	−0.54%
Sidewall height	5.50 in (139.8 mm)	4.43 in (112.5 mm)	−1.07 in (−27.2 mm)	−19.50%
Section width	8.46 in (215.0 mm)	8.86 in (225.0 mm)	+0.39 in (+10.0 mm)	+4.65%
Circumference	84.84 in (2,154.8 mm)	84.38 in (2,143.2 mm)	−0.46 in (−11.6 mm)	−0.54%
Revolutions per mile	747	751	+4	+0.54%

True speed with the speedometer calibrated for 215/65R16
Indicated	Actual on 215/65R16	Actual on 225/50R18	Difference
30 mph	30.0 mph	29.8 mph	−0.2 mph
60 mph	60.0 mph	59.7 mph	−0.3 mph
75 mph	75.0 mph	74.6 mph	−0.4 mph

Ride-height change: 225/50R18 lowers the vehicle by 0.07 in (1.8 mm) at the axle (half the −3.7 mm diameter difference).

225/50R18 is 0.15 in shorter than 215/65R16 and 10 mm wider, a 0.54% difference in overall diameter.

With the speedometer calibrated for 215/65R16, an indicated 60 mph is actually 59.7 mph on 225/50R18, and revolutions per mile change from 747 to 751.

225/50R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 215/65R16.

Size pages

Other comparisons with 215/65R16

Other comparisons with 225/50R18

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