GarageCalc What 255/65R16 means
255 is the section width in millimeters (10.0 in). 65 is the aspect ratio: the sidewall is 65 percent of the width, so 255 × 0.65 = 166 mm (6.5 in). R is radial construction, and 16 is the wheel diameter in inches (406 mm). Stack two sidewalls on the wheel and you get the overall diameter: 406 + 2 × 166 = 738 mm, or 29.1 in.
A full marking adds a load index and speed rating after the size, for example 255/65R16 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 255/65R16
Going up one wheel size, the closest match is 255/60R17 at -0.0% diameter with a 153 mm sidewall instead of 166 mm. Going down one size, 255/70R15 is +0.0% with a taller 179 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.
Frequently asked questions
How tall is a 255/65R16 tire?
29.1 inches (738 mm) in overall diameter: the 16-inch wheel (406 mm) plus two 166 mm sidewalls. Real tires land within about 1 to 2 percent of that depending on brand, tread depth and pressure.
What is 255/65R16 in inches?
29.1 x 10.0 R16: 29.1 inches tall, 10.0 inches wide, on a 16-inch wheel. The sidewall is 6.5 inches and the circumference is 91.3 inches, so the tire turns 694 times per mile.
What tire sizes are equivalent to 255/65R16?
Within 3 percent of the same diameter on the same 16-inch wheel: 235/70R16 (-0.3%), 245/70R16 (+1.6%), 235/75R16 (+2.8%); on a 17-inch wheel: 255/60R17 (-0.0%), 235/65R17 (-0.1%); on a 15-inch wheel: 255/70R15 (+0.0%), 235/75R15 (-0.6%). The percentage is the diameter change, which is also your speedometer error.