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205/55R16 vs 215/40R18 tire size comparison

205/55R16215/40R18

215/40R18 is 0.1 in (0.43%) shorter than 205/55R16 and 0.4 in wider. They fit different wheels: 205/55R16 a 16-inch wheel and 215/40R18 an 18-inch wheel.

205/55R16 and 215/40R18 side by side

-0.1 in / -0.43%205/55R16: 24.9 in tall, solid line215/40R18: 24.8 in tall, dashed line205/55R16Width 8.1 in (205 mm)Sidewall 4.4 in (113 mm)215/40R18Width 8.5 in (215 mm)Sidewall 3.4 in (86 mm)
205/55R16 is drawn with a solid line and 215/40R18 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 205/55R16 and 215/40R18, with the difference (215/40R18 minus 205/55R16)
Measurement205/55R16215/40R18DifferenceDifference %
Section width8.1 in (205 mm)8.5 in (215 mm)+0.4 in (+10 mm)+4.88%
Sidewall height4.4 in (113 mm)3.4 in (86 mm)-1.0 in (-27 mm)-23.73%
Wheel (rim) diameter16.0 in (406 mm)18.0 in (457 mm)+2.0 in (+51 mm)+12.50%
Overall diameter24.9 in (632 mm)24.8 in (629 mm)-0.1 in (-3 mm)-0.43%
Circumference78.2 in (1985 mm)77.8 in (1977 mm)-0.4 in (-8 mm)-0.43%
Revolutions per mile811814+3+0.43%

Differences are 215/40R18 minus 205/55R16; percentages are relative to 205/55R16. These are nominal design dimensions. Real tires vary by brand, tread depth, wheel width, load and pressure.

The overall diameter differs by 0.43%, 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 205/55R16, the actual speed on 215/40R18 is about 59.7 mph. When it reads 60 mph on a vehicle built for 215/40R18, the actual speed on 205/55R16 is about 60.3 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, 205/55R16 against 215/40R18
Speedometer readsActual on 215/40R18 (built for 205/55R16)Actual on 205/55R16 (built for 215/40R18)
20 mph19.9 mph20.1 mph
30 mph29.9 mph30.1 mph
40 mph39.8 mph40.2 mph
50 mph49.8 mph50.2 mph
60 mph59.7 mph60.3 mph
70 mph69.7 mph70.3 mph
80 mph79.7 mph80.3 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 205/55R16 or 215/40R18 tires

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Other comparisons with 205/55R16

Side-by-side dimensions and speedometer difference for sizes close to 205/55R16 in overall diameter.

Other comparisons with 215/40R18

Side-by-side dimensions and speedometer difference for sizes close to 215/40R18 in overall diameter.

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