275/30R18 Tire Size in Inches

24.5" tall, 10.8" wide, 3.2" sidewall

Diameter24.5"622 mm
Overall diameter24.5"622 mm
Section width10.8"275 mm
Sidewall height3.2"83 mm
Circumference77.0"1955 mm
Revolutions per mile823512 per km
Wheel diameter18"≈ 24.5x10.8R18 in inches

A 275/30R18 tire is 24.5 inches (622 mm) tall and 10.8 inches wide. The sidewall is 30% of the width, 3.2 inches, on a 18-inch wheel, and the tire turns about 823 times per mile.

In flotation terms that is about 24.5x10.8R18. People often call it a 24-inch tire.

The size most often compared with it is 285/30R18, which is 0.2" taller (+1.0%). At an indicated 60 mph you would be doing 60.6 mph on it.

275/30R18
285/30R18
Diameter difference+0.96%diameter 24.50" → 24.73"
CurrentNew
CurrentNewDifference

Speedometer

ShowsActual speed

Gear ratio to match

–enter your current axle ratio

Sizes near 275/30R18

Same 18" wheel, within 20 mm of width and 10 points of aspect ratio.

SizeDiameterWidthSidewallvs 275/30R18
285/30R1824.7"11.2"3.4"+1.0%
295/30R1825.0"11.6"3.5"+1.9%
255/35R1825.0"10.0"3.5"+2.2%
265/35R1825.3"10.4"3.7"+3.3%
275/35R1825.6"10.8"3.8"+4.4%
285/35R1825.9"11.2"3.9"+5.5%
255/40R1826.0"10.0"4.0"+6.3%
295/35R1826.1"11.6"4.1"+6.7%
265/40R1826.3"10.4"4.2"+7.6%
275/40R1826.7"10.8"4.3"+8.8%

Same height on a different wheel

Sizes within 2% of 24.5" on 16" or 17" wheels.

SizeDiameterWidthSidewallvs 275/30R18
215/50R1624.5"8.5"4.2"−0.1%
275/35R1724.6"10.8"3.8"+0.3%
235/40R1724.4"9.3"3.7"−0.4%
245/40R1724.7"9.6"3.9"+0.9%
225/50R1624.9"8.9"4.4"+1.5%
205/50R1624.1"8.1"4.0"−1.7%

Speedometer with a different size

Actual speed when the speedometer is calibrated for 275/30R18.

Speedometer showson 285/30R18on 295/30R18on 255/35R18
30 mph30.3 mph30.6 mph30.7 mph
45 mph45.4 mph45.9 mph46.0 mph
60 mph60.6 mph61.2 mph61.3 mph
70 mph70.7 mph71.4 mph71.5 mph

275/30R18 FAQ

How tall is a 275/30R18 tire?

24.5 inches (622 mm). The sidewall is 3.2 inches.

How wide is a 275/30R18 tire?

10.8 inches (275 mm) section width, measured sidewall to sidewall.

What is 275/30R18 in flotation size?

About 24.5x10.8R18.

Can I use 285/30R18 instead of 275/30R18?

285/30R18 is +1.0% in diameter, within the common 3% guideline. It is 0.4" wider.