215/50R18 vs 225/50R18

225/50R18 is 0.39 in (10.0 mm) taller than 215/50R18, a +1.49% diameter difference. With the speedometer set for 215/50R18, an indicated 60 mph is 60.9 mph on 225/50R18.

Is this a safe swap?

Diameter difference +1.49%: within the ±3% guideline

By overall diameter alone, 225/50R18 falls inside the ±3% range commonly used as a guideline when replacing 215/50R18. 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.

215/50R18 vs 225/50R18 differences
Measurement	215/50R18	225/50R18	Difference	% diff
Overall diameter	26.46 in (672.2 mm)	26.86 in (682.2 mm)	+0.39 in (+10.0 mm)	+1.49%
Sidewall height	4.23 in (107.5 mm)	4.43 in (112.5 mm)	+0.20 in (+5.0 mm)	+4.65%
Section width	8.46 in (215.0 mm)	8.86 in (225.0 mm)	+0.39 in (+10.0 mm)	+4.65%
Circumference	83.14 in (2,111.8 mm)	84.38 in (2,143.2 mm)	+1.24 in (+31.4 mm)	+1.49%
Revolutions per mile	762	751	−11	−1.47%

True speed with the speedometer calibrated for 215/50R18
Indicated	Actual on 215/50R18	Actual on 225/50R18	Difference
30 mph	30.0 mph	30.4 mph	+0.4 mph
60 mph	60.0 mph	60.9 mph	+0.9 mph
75 mph	75.0 mph	76.1 mph	+1.1 mph

Ride-height change: 225/50R18 raises the vehicle by 0.20 in (5.0 mm) at the axle (half the +10.0 mm diameter difference).

225/50R18 is 0.39 in taller than 215/50R18 and 10 mm wider, a 1.49% difference in overall diameter.

With the speedometer calibrated for 215/50R18, an indicated 60 mph is actually 60.9 mph on 225/50R18, and revolutions per mile change from 762 to 751.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 215/50R18

Other comparisons with 225/50R18

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