265/40R18 tire size in inches

A 265/40R18 tire measures

26.3" tall × 10.4" wide

4.17" sidewall on a 18" wheel. 765 revolutions per mile.

265/40R18 means a tire 265 mm wide, with sidewalls 40% as tall as the tire is wide (106 mm), radial construction (R), for a 18 inch wheel.

26.3"18" rim4.2"10.4" wide
265/40R18: 26.3 inches tall, 10.4 inches wide, on a 18 inch rim, drawn to scale

265/40R18 specs

Overall diameter (height)26.35 inches (669 mm)
Section width10.43 inches (265 mm)
Sidewall height4.17 inches (106 mm)
Wheel (rim) diameter18 inches
Circumference82.8 inches (2,102 mm)
Revolutions per mile765
Revolutions per kilometer476
Approximate rim width8.5" to 10.0"
In inches (flotation style)26.3x10.4R18
Aspect ratio40%

Calculated from the size. Real tires differ by brand, model and tread depth, typically by a few tenths of an inch.

Sizes that can replace 265/40R18 on a 18" wheel

These 18" sizes are within 3% of 265/40R18's overall diameter, the range most tire shops treat as interchangeable.

SizeDiameterWidthDifferenceReal speed at 60
235/45R1826.33"9.25"−0.1%60.0 mphCompare
305/35R1826.41"12.01"+0.2%60.1 mphCompare
195/55R1826.44"7.68"+0.4%60.2 mphCompare
215/50R1826.46"8.46"+0.4%60.3 mphCompare
295/35R1826.13"11.61"−0.8%59.5 mphCompare
205/50R1826.07"8.07"−1.0%59.4 mphCompare
255/40R1826.03"10.04"−1.2%59.3 mphCompare
275/40R1826.66"10.83"+1.2%60.7 mphCompare
245/45R1826.68"9.65"+1.3%60.8 mphCompare
315/35R1826.68"12.40"+1.3%60.8 mphCompare
225/45R1825.97"8.86"−1.4%59.1 mphCompare
285/35R1825.85"11.22"−1.9%58.9 mphCompare

Same height on other wheel sizes (plus and minus sizing)

SizeWheelDiameterDifference
175/75R1616"26.33"0.0%Compare
225/30R2121"26.31"−0.1%Compare
185/85R1414"26.38"+0.1%Compare
215/55R1717"26.31"−0.1%Compare
265/35R1919"26.30"−0.2%Compare
265/45R1717"26.39"+0.2%Compare
205/70R1515"26.30"−0.2%Compare
325/25R2020"26.40"+0.2%Compare
295/40R1717"26.29"−0.2%Compare
225/70R1414"26.40"+0.2%Compare
235/40R1919"26.40"+0.2%Compare
225/75R1313"26.29"−0.2%Compare

One size up or down

Compare 265/40R18 with another size

With 275/40R18 tires, when your speedometer says 60 mph you are really going

60.7 mph

275/40R18 is +0.31 inches (+1.2%) in overall diameter. That is within the 3% most shops and makers allow.

265/40R18275/40R18Difference%
Overall diameter26.35"26.66"+0.31"+1.2%
Section width10.43"10.83"+0.39"+3.8%
Sidewall height4.17"4.33"+0.16"+3.8%
Circumference82.77"83.76"+0.99"+1.2%
Revolutions per mile765.5756.5−9.0−1.2%

Questions

How tall is a 265/40R18 tire?
A 265/40R18 tire is 26.3 inches tall (669 mm), calculated from the size. It is 10.4 inches wide with 4.2 inches sidewalls. Real tires vary by a few tenths of an inch between brands and tread patterns.
What does 265/40R18 mean?
265/40R18 means a tire 265 mm wide, with sidewalls 40% as tall as the tire is wide (106 mm), radial construction (R), for a 18 inch wheel.
How many revolutions per mile does a 265/40R18 tire make?
About 765 revolutions per mile, based on a circumference of 82.8 inches. Under load the tire flattens slightly, so the maker's published figure is usually a little higher.
What rim width fits a 265/40R18 tire?
Roughly 8.5" to 10.0". Check the tire maker's approved rim range for the exact model before buying wheels.
Can I use 235/45R18 instead of 265/40R18?
235/45R18 is −0.02 inches (−0.1%) in overall diameter, so at an indicated 60 mph you would be doing 60.0 mph. Differences under 3% are usually fine, but check clearance, load index and your vehicle's placard.

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