255/50R18 Tire Size in Inches

28.0" tall, 10.0" wide, 5.0" sidewall

Diameter28.0"712 mm
Overall diameter28.0"712 mm
Section width10.0"255 mm
Sidewall height5.0"128 mm
Circumference88.1"2237 mm
Revolutions per mile719447 per km
Wheel diameter18"≈ 28.0x10.0R18 in inches

A 255/50R18 tire is 28.0 inches (712 mm) tall and 10.0 inches wide. The sidewall is 50% of the width, 5.0 inches, on a 18-inch wheel, and the tire turns about 719 times per mile.

In flotation terms that is about 28.0x10.0R18. People often call it a 28-inch tire.

The size most often compared with it is 275/45R18, which is 0.3" shorter (−1.1%). At an indicated 60 mph you would be doing 59.4 mph on it.

255/50R18
275/45R18
Diameter difference−1.05%diameter 28.04" → 27.74"
CurrentNew
CurrentNewDifference

Speedometer

ShowsActual speed

Gear ratio to match

–enter your current axle ratio

Sizes near 255/50R18

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

SizeDiameterWidthSidewallvs 255/50R18
275/45R1827.7"10.8"4.9"−1.1%
265/50R1828.4"10.4"5.2"+1.4%
275/50R1828.8"10.8"5.4"+2.8%
255/45R1827.0"10.0"4.5"−3.6%
275/40R1826.7"10.8"4.3"−4.9%
265/55R1829.5"10.4"5.7"+5.1%
265/40R1826.3"10.4"4.2"−6.0%
275/55R1829.9"10.8"6.0"+6.7%
255/40R1826.0"10.0"4.0"−7.2%
275/60R1831.0"10.8"6.5"+10.5%

Same height on a different wheel

Sizes within 2% of 28.0" on 20" or 17" wheels.

SizeDiameterWidthSidewallvs 255/50R18
295/35R2028.1"11.6"4.1"+0.3%
345/30R2028.1"13.6"4.1"+0.4%
285/35R2027.9"11.2"3.9"−0.7%
275/50R1727.8"10.8"5.4"−0.8%
245/55R1727.6"9.6"5.3"−1.5%
275/35R2027.6"10.8"3.8"−1.6%

Speedometer with a different size

Actual speed when the speedometer is calibrated for 255/50R18.

Speedometer showson 275/45R18on 265/50R18on 275/50R18
30 mph29.7 mph30.4 mph30.8 mph
45 mph44.5 mph45.6 mph46.3 mph
60 mph59.4 mph60.8 mph61.7 mph
70 mph69.3 mph71.0 mph72.0 mph

255/50R18 FAQ

How tall is a 255/50R18 tire?

28.0 inches (712 mm). The sidewall is 5.0 inches.

How wide is a 255/50R18 tire?

10.0 inches (255 mm) section width, measured sidewall to sidewall.

What is 255/50R18 in flotation size?

About 28.0x10.0R18.

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

275/45R18 is −1.1% in diameter, within the common 3% guideline. It is 0.8" wider.