225/40R16 vs 205/45R16

205/45R16 is 0.18 in (4.5 mm) taller than 225/40R16, a +0.77% diameter difference. With the speedometer set for 225/40R16, an indicated 60 mph is 60.5 mph on 205/45R16.

Is this a safe swap?

Diameter difference +0.77%: under 1%

By overall diameter alone, 205/45R16 is a near match for 225/40R16; 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.

225/40R16 vs 205/45R16 differences
Measurement	225/40R16	205/45R16	Difference	% diff
Overall diameter	23.09 in (586.4 mm)	23.26 in (590.9 mm)	+0.18 in (+4.5 mm)	+0.77%
Sidewall height	3.54 in (90.0 mm)	3.63 in (92.3 mm)	+0.09 in (+2.3 mm)	+2.50%
Section width	8.86 in (225.0 mm)	8.07 in (205.0 mm)	−0.79 in (−20.0 mm)	−8.89%
Circumference	72.53 in (1,842.2 mm)	73.09 in (1,856.4 mm)	+0.56 in (+14.1 mm)	+0.77%
Revolutions per mile	874	867	−7	−0.76%

True speed with the speedometer calibrated for 225/40R16
Indicated	Actual on 225/40R16	Actual on 205/45R16	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.5 mph	+0.5 mph
75 mph	75.0 mph	75.6 mph	+0.6 mph

Ride-height change: 205/45R16 raises the vehicle by 0.09 in (2.3 mm) at the axle (half the +4.5 mm diameter difference).

205/45R16 is 0.18 in taller than 225/40R16 and 20 mm narrower, a 0.77% difference in overall diameter.

With the speedometer calibrated for 225/40R16, an indicated 60 mph is actually 60.5 mph on 205/45R16, and revolutions per mile change from 874 to 867.

Both sizes mount on 16-inch wheels.

Size pages

Other comparisons with 225/40R16

Other comparisons with 205/45R16

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