275/45R18 Tire Size in Inches

27.7" tall, 10.8" wide, 4.9" sidewall

Diameter27.7"705 mm
Overall diameter27.7"705 mm
Section width10.8"275 mm
Sidewall height4.9"124 mm
Circumference87.2"2214 mm
Revolutions per mile727452 per km
Wheel diameter18"≈ 27.7x10.8R18 in inches

A 275/45R18 tire is 27.7 inches (705 mm) tall and 10.8 inches wide. The sidewall is 45% of the width, 4.9 inches, on a 18-inch wheel, and the tire turns about 727 times per mile.

In flotation terms that is about 27.7x10.8R18. People often call it a 28-inch tire.

The size most often compared with it is 255/50R18, which is 0.3" taller (+1.1%). At an indicated 60 mph you would be doing 60.6 mph on it.

275/45R18
255/50R18
Diameter difference+1.06%diameter 27.74" → 28.04"
CurrentNew
CurrentNewDifference

Speedometer

ShowsActual speed

Gear ratio to match

–enter your current axle ratio

Sizes near 275/45R18

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

SizeDiameterWidthSidewallvs 275/45R18
255/50R1828.0"10.0"5.0"+1.1%
285/45R1828.1"11.2"5.0"+1.3%
295/40R1827.3"11.6"4.6"−1.6%
265/50R1828.4"10.4"5.2"+2.5%
255/45R1827.0"10.0"4.5"−2.6%
295/45R1828.5"11.6"5.2"+2.6%
285/40R1827.0"11.2"4.5"−2.8%
275/50R1828.8"10.8"5.4"+3.9%
275/40R1826.7"10.8"4.3"−3.9%
265/40R1826.3"10.4"4.2"−5.0%

Same height on a different wheel

Sizes within 2% of 27.7" on 17" or 20" wheels.

SizeDiameterWidthSidewallvs 275/45R18
275/50R1727.8"10.8"5.4"+0.3%
285/35R2027.9"11.2"3.9"+0.4%
245/55R1727.6"9.6"5.3"−0.5%
275/35R2027.6"10.8"3.8"−0.6%
205/65R1727.5"8.1"5.2"−0.9%
265/50R1727.4"10.4"5.2"−1.1%

Speedometer with a different size

Actual speed when the speedometer is calibrated for 275/45R18.

Speedometer showson 255/50R18on 285/45R18on 295/40R18
30 mph30.3 mph30.4 mph29.5 mph
45 mph45.5 mph45.6 mph44.3 mph
60 mph60.6 mph60.8 mph59.0 mph
70 mph70.7 mph70.9 mph68.9 mph

275/45R18 FAQ

How tall is a 275/45R18 tire?

27.7 inches (705 mm). The sidewall is 4.9 inches.

How wide is a 275/45R18 tire?

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

What is 275/45R18 in flotation size?

About 27.7x10.8R18.

Can I use 255/50R18 instead of 275/45R18?

255/50R18 is +1.1% in diameter, within the common 3% guideline. It is 0.8" narrower.