205/65R16 vs 245/45R18

245/45R18 is 0.19 in (4.8 mm) taller than 205/65R16, a +0.71% diameter difference. With the speedometer set for 205/65R16, an indicated 60 mph is 60.4 mph on 245/45R18.

Is this a safe swap?

Diameter difference +0.71%: under 1%

By overall diameter alone, 245/45R18 is a near match for 205/65R16; 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.

205/65R16 vs 245/45R18 differences
Measurement	205/65R16	245/45R18	Difference	% diff
Overall diameter	26.49 in (672.9 mm)	26.68 in (677.7 mm)	+0.19 in (+4.8 mm)	+0.71%
Sidewall height	5.25 in (133.3 mm)	4.34 in (110.3 mm)	−0.91 in (−23.0 mm)	−17.26%
Section width	8.07 in (205.0 mm)	9.65 in (245.0 mm)	+1.57 in (+40.0 mm)	+19.51%
Circumference	83.23 in (2,114.0 mm)	83.82 in (2,129.1 mm)	+0.59 in (+15.1 mm)	+0.71%
Revolutions per mile	761	756	−5	−0.71%

True speed with the speedometer calibrated for 205/65R16
Indicated	Actual on 205/65R16	Actual on 245/45R18	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.4 mph	+0.4 mph
75 mph	75.0 mph	75.5 mph	+0.5 mph

Ride-height change: 245/45R18 raises the vehicle by 0.09 in (2.4 mm) at the axle (half the +4.8 mm diameter difference).

245/45R18 is 0.19 in taller than 205/65R16 and 40 mm wider, a 0.71% difference in overall diameter.

With the speedometer calibrated for 205/65R16, an indicated 60 mph is actually 60.4 mph on 245/45R18, and revolutions per mile change from 761 to 756.

245/45R18 mounts on a 18-inch wheel, a plus-2 fitment from the 16-inch wheel of 205/65R16.

Size pages

Other comparisons with 205/65R16

Other comparisons with 245/45R18

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