315/35R18 tire size in inches

A 315/35R18 tire measures

26.7" tall × 12.4" wide

4.34" sidewall on a 18" wheel. 756 revolutions per mile.

315/35R18 means a tire 315 mm wide, with sidewalls 35% as tall as the tire is wide (110 mm), radial construction (R), for a 18 inch wheel.

26.7"18" rim4.3"12.4" wide
315/35R18: 26.7 inches tall, 12.4 inches wide, on a 18 inch rim, drawn to scale

315/35R18 specs

Overall diameter (height)26.68 inches (678 mm)
Section width12.40 inches (315 mm)
Sidewall height4.34 inches (110 mm)
Wheel (rim) diameter18 inches
Circumference83.8 inches (2,129 mm)
Revolutions per mile756
Revolutions per kilometer470
Approximate rim width10.5" to 12.0"
In inches (flotation style)26.7x12.4R18
Aspect ratio35%

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 315/35R18 on a 18" wheel

These 18" sizes are within 3% of 315/35R18's overall diameter, the range most tire shops treat as interchangeable.

SizeDiameterWidthDifferenceReal speed at 60
245/45R1826.68"9.65"0.0%60.0 mphCompare
275/40R1826.66"10.83"−0.1%60.0 mphCompare
225/50R1826.86"8.86"+0.7%60.4 mphCompare
205/55R1826.88"8.07"+0.7%60.4 mphCompare
215/50R1826.46"8.46"−0.8%59.5 mphCompare
195/55R1826.44"7.68"−0.9%59.5 mphCompare
305/35R1826.41"12.01"−1.0%59.4 mphCompare
325/35R1826.96"12.80"+1.0%60.6 mphCompare
285/40R1826.98"11.22"+1.1%60.7 mphCompare
265/40R1826.35"10.43"−1.3%59.2 mphCompare
255/45R1827.04"10.04"+1.3%60.8 mphCompare
235/45R1826.33"9.25"−1.3%59.2 mphCompare

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

SizeWheelDiameterDifference
205/60R1717"26.69"0.0%Compare
325/30R1919"26.68"0.0%Compare
215/75R1414"26.70"+0.1%Compare
185/80R1515"26.65"−0.1%Compare
175/85R1515"26.71"+0.1%Compare
245/50R1717"26.65"−0.1%Compare
245/40R1919"26.72"+0.1%Compare
205/85R1313"26.72"+0.1%Compare
285/30R2020"26.73"+0.2%Compare
225/60R1616"26.63"−0.2%Compare
235/25R2222"26.63"−0.2%Compare
215/45R1919"26.62"−0.2%Compare

One size up or down

Compare 315/35R18 with another size

With 325/35R18 tires, when your speedometer says 60 mph you are really going

60.6 mph

325/35R18 is +0.28 inches (+1.0%) in overall diameter. That is within the 3% most shops and makers allow.

315/35R18325/35R18Difference%
Overall diameter26.68"26.96"+0.28"+1.0%
Section width12.40"12.80"+0.39"+3.2%
Sidewall height4.34"4.48"+0.14"+3.2%
Circumference83.82"84.69"+0.87"+1.0%
Revolutions per mile755.9748.2−7.7−1.0%

Questions

How tall is a 315/35R18 tire?
A 315/35R18 tire is 26.7 inches tall (678 mm), calculated from the size. It is 12.4 inches wide with 4.3 inches sidewalls. Real tires vary by a few tenths of an inch between brands and tread patterns.
What does 315/35R18 mean?
315/35R18 means a tire 315 mm wide, with sidewalls 35% as tall as the tire is wide (110 mm), radial construction (R), for a 18 inch wheel.
How many revolutions per mile does a 315/35R18 tire make?
About 756 revolutions per mile, based on a circumference of 83.8 inches. Under load the tire flattens slightly, so the maker's published figure is usually a little higher.
What rim width fits a 315/35R18 tire?
Roughly 10.5" to 12.0". Check the tire maker's approved rim range for the exact model before buying wheels.
Can I use 245/45R18 instead of 315/35R18?
245/45R18 is 0.00 inches (0.0%) 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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