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225/60R18 vs 275/40R20 tire size comparison

225/60R18275/40R20

275/40R20 is 0.1 in (0.11%) taller than 225/60R18 and 1.9 in wider. They fit different wheels: 225/60R18 an 18-inch wheel and 275/40R20 a 20-inch wheel.

225/60R18 and 275/40R20 side by side

+0.1 in / +0.11%225/60R18: 28.6 in tall, solid line275/40R20: 28.7 in tall, dashed line225/60R18Width 8.9 in (225 mm)Sidewall 5.3 in (135 mm)275/40R20Width 10.8 in (275 mm)Sidewall 4.3 in (110 mm)
225/60R18 is drawn with a solid line and 275/40R20 with a dashed line. In each drawing both tires are to the same scale; the tread shoulder and bead curves are simplified. The table below has the same numbers.
Dimensions of 225/60R18 and 275/40R20, with the difference (275/40R20 minus 225/60R18)
Measurement225/60R18275/40R20DifferenceDifference %
Section width8.9 in (225 mm)10.8 in (275 mm)+1.9 in (+50 mm)+22.22%
Sidewall height5.3 in (135 mm)4.3 in (110 mm)-1.0 in (-25 mm)-18.52%
Wheel (rim) diameter18.0 in (457 mm)20.0 in (508 mm)+2.0 in (+51 mm)+11.11%
Overall diameter28.6 in (727 mm)28.7 in (728 mm)+0.1 in (+1 mm)+0.11%
Circumference89.9 in (2285 mm)90.0 in (2287 mm)+0.1 in (+2 mm)+0.11%
Revolutions per mile7047040-0.11%

Differences are 275/40R20 minus 225/60R18; percentages are relative to 225/60R18. These are nominal design dimensions. Real tires vary by brand, tread depth, wheel width, load and pressure.

The overall diameter differs by 0.11%, which is within the common 3% rule of thumb.

The rule of thumb keeps a replacement size within about 3% of the original overall diameter. It covers diameter only. It is not a fit, load or safety check, because width, wheel diameter, load capacity and clearance matter too. Confirm any size change with your vehicle's owner's manual or a tire professional.

Speedometer difference

When the speedometer reads 60 mph on a vehicle built for 225/60R18, the actual speed on 275/40R20 is about 60.1 mph. When it reads 60 mph on a vehicle built for 275/40R20, the actual speed on 225/60R18 is about 59.9 mph. These figures assume the speedometer is accurate on the original size and use nominal dimensions, so treat them as estimates.

Actual speed for a given speedometer reading, 225/60R18 against 275/40R20
Speedometer readsActual on 275/40R20 (built for 225/60R18)Actual on 225/60R18 (built for 275/40R20)
20 mph20.0 mph20.0 mph
30 mph30.0 mph30.0 mph
40 mph40.0 mph40.0 mph
50 mph50.1 mph49.9 mph
60 mph60.1 mph59.9 mph
70 mph70.1 mph69.9 mph
80 mph80.1 mph79.9 mph

A common rule of thumb is to keep a replacement size within about 3% of the original overall diameter. Check the tire placard on the driver's door jamb and your owner's manual for the sizes your vehicle was built for. Confirm any size change with your vehicle's owner's manual or a tire professional.

Which vehicles use each size?

These vehicles list the size among their verified sizes, by trim. Open one to see all of its sizes.

Check it in the calculator

The calculator takes the same two sizes and shows the full comparison, or lets you swap either one for another size.

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Shop for 225/60R18 or 275/40R20 tires

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Other comparisons with 225/60R18

Side-by-side dimensions and speedometer difference for sizes close to 225/60R18 in overall diameter.

Other comparisons with 275/40R20

Side-by-side dimensions and speedometer difference for sizes close to 275/40R20 in overall diameter.

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