235/65R18 tire size in inches

A 235/65R18 tire measures

30.0" tall × 9.3" wide

6.01" sidewall on a 18" wheel. 672 revolutions per mile.

235/65R18 means a tire 235 mm wide, with sidewalls 65% as tall as the tire is wide (153 mm), radial construction (R), for a 18 inch wheel.

30.0"18" rim6.0"9.3" wide
235/65R18: 30.0 inches tall, 9.3 inches wide, on a 18 inch rim, drawn to scale

235/65R18 specs

Overall diameter (height)30.03 inches (763 mm)
Section width9.25 inches (235 mm)
Sidewall height6.01 inches (153 mm)
Wheel (rim) diameter18 inches
Circumference94.3 inches (2,396 mm)
Revolutions per mile672
Revolutions per kilometer417
Approximate rim width6.0" to 7.5"
In inches (flotation style)30.0x9.3R18
Aspect ratio65%

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 235/65R18 on a 18" wheel

These 18" sizes are within 3% of 235/65R18's overall diameter, the range most tire shops treat as interchangeable.

SizeDiameterWidthDifferenceReal speed at 60
255/60R1830.05"10.04"+0.1%60.0 mphCompare
305/50R1830.01"12.01"−0.1%60.0 mphCompare
205/75R1830.11"8.07"+0.3%60.2 mphCompare
275/55R1829.91"10.83"−0.4%59.8 mphCompare
335/45R1829.87"13.19"−0.5%59.7 mphCompare
215/70R1829.85"8.46"−0.6%59.6 mphCompare
285/55R1830.34"11.22"+1.0%60.6 mphCompare
225/70R1830.40"8.86"+1.2%60.7 mphCompare
315/50R1830.40"12.40"+1.2%60.7 mphCompare
295/50R1829.61"11.61"−1.4%59.2 mphCompare
245/60R1829.57"9.65"−1.5%59.1 mphCompare
265/60R1830.52"10.43"+1.6%61.0 mphCompare

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

SizeWheelDiameterDifference
255/40R2222"30.03"0.0%Compare
255/30R2424"30.02"0.0%Compare
255/45R2121"30.04"0.0%Compare
255/50R2020"30.04"0.0%Compare
255/55R1919"30.04"+0.1%Compare
215/65R1919"30.00"−0.1%Compare
255/65R1717"30.05"+0.1%Compare
305/25R2424"30.00"−0.1%Compare
30x9.50R1515"30.00"−0.1%Compare
255/70R1616"30.06"+0.1%Compare
225/85R1515"30.06"+0.1%Compare
255/75R1515"30.06"+0.1%Compare

One size up or down

Compare 235/65R18 with another size

With 245/65R18 tires, when your speedometer says 60 mph you are really going

61.0 mph

245/65R18 is +0.51 inches (+1.7%) in overall diameter. That is within the 3% most shops and makers allow.

235/65R18245/65R18Difference%
Overall diameter30.03"30.54"+0.51"+1.7%
Section width9.25"9.65"+0.39"+4.3%
Sidewall height6.01"6.27"+0.26"+4.3%
Circumference94.33"95.94"+1.61"+1.7%
Revolutions per mile671.7660.4−11.3−1.7%

Questions

How tall is a 235/65R18 tire?
A 235/65R18 tire is 30.0 inches tall (763 mm), calculated from the size. It is 9.3 inches wide with 6.0 inches sidewalls. Real tires vary by a few tenths of an inch between brands and tread patterns.
What does 235/65R18 mean?
235/65R18 means a tire 235 mm wide, with sidewalls 65% as tall as the tire is wide (153 mm), radial construction (R), for a 18 inch wheel.
How many revolutions per mile does a 235/65R18 tire make?
About 672 revolutions per mile, based on a circumference of 94.3 inches. Under load the tire flattens slightly, so the maker's published figure is usually a little higher.
What rim width fits a 235/65R18 tire?
Roughly 6.0" to 7.5". Check the tire maker's approved rim range for the exact model before buying wheels.
Can I use 255/60R18 instead of 235/65R18?
255/60R18 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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