GarageCalc What 265/65R18 means
265 is the section width in millimeters (10.4 in). 65 is the aspect ratio: the sidewall is 65 percent of the width, so 265 × 0.65 = 172 mm (6.8 in). R is radial construction, and 18 is the wheel diameter in inches (457 mm). Stack two sidewalls on the wheel and you get the overall diameter: 457 + 2 × 172 = 802 mm, or 31.6 in.
A full marking adds a load index and speed rating after the size, for example 265/65R18 91V. Those two codes set how much weight and speed the tire is certified for; look them up in the load index chart and the speed rating chart.
Plus and minus sizing from 265/65R18
Going up one wheel size, the closest match is 275/55R19 at -2.1% diameter with a 151 mm sidewall instead of 172 mm. Going down one size, 265/70R17 is +0.1% with a taller 186 mm sidewall for more comfort and pothole margin. Anything inside 3 percent keeps the speedometer, ABS and gearing effectively stock; the comparison calculator shows the full speedometer table for any pair.
Which cars come with 265/65R18
Typical factory fitments include Chevrolet Silverado 1500 LT (2019 on) and GMC Sierra 1500 (2019 on). Tire size changes with trim and wheel option, so confirm on the door-jamb placard before buying.
Frequently asked questions
How tall is a 265/65R18 tire?
31.6 inches (802 mm) in overall diameter: the 18-inch wheel (457 mm) plus two 172 mm sidewalls. Real tires land within about 1 to 2 percent of that depending on brand, tread depth and pressure.
What is 265/65R18 in inches?
31.6 x 10.4 R18: 31.6 inches tall, 10.4 inches wide, on an 18-inch wheel. The sidewall is 6.8 inches and the circumference is 99.2 inches, so the tire turns 639 times per mile.
What tire sizes are equivalent to 265/65R18?
Within 3 percent of the same diameter on the same 18-inch wheel: 245/70R18 (-0.2%), 285/60R18 (-0.3%), 255/70R18 (+1.6%); on a 19-inch wheel: 275/55R19 (-2.1%); on a 17-inch wheel: 265/70R17 (+0.1%), 245/75R17 (-0.3%). The percentage is the diameter change, which is also your speedometer error.
Can I use 275/65R18 instead of 265/65R18?
Dimensionally yes: 275/65R18 is 1.6% taller (+13 mm) and 10 mm wider, and at a true 60 mph the speedometer would read 59.0 mph. The extra width needs about 0.20 in of clearance on each side of the tire and a rim width that suits 275 mm.