GarageCalc What 205/65R15 means
205 is the section width in millimeters (8.1 in). 65 is the aspect ratio: the sidewall is 65 percent of the width, so 205 × 0.65 = 133 mm (5.2 in). R is radial construction, and 15 is the wheel diameter in inches (381 mm). Stack two sidewalls on the wheel and you get the overall diameter: 381 + 2 × 133 = 648 mm, or 25.5 in.
A full marking adds a load index and speed rating after the size, for example 205/65R15 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 205/65R15
Going up one wheel size, the closest match is 215/55R16 at -0.7% diameter with a 118 mm sidewall instead of 133 mm. Going down one size, 205/70R14 is -0.8% with a taller 144 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 205/65R15 tire?
25.5 inches (648 mm) in overall diameter: the 15-inch wheel (381 mm) plus two 133 mm sidewalls. Real tires land within about 1 to 2 percent of that depending on brand, tread depth and pressure.
What is 205/65R15 in inches?
25.5 x 8.1 R15: 25.5 inches tall, 8.1 inches wide, on a 15-inch wheel. The sidewall is 5.2 inches and the circumference is 80.1 inches, so the tire turns 791 times per mile.
What tire sizes are equivalent to 205/65R15?
Within 3 percent of the same diameter on the same 15-inch wheel: 225/60R15 (+0.5%), 195/70R15 (+1.0%), 215/60R15 (-1.3%); on a 16-inch wheel: 215/55R16 (-0.7%), 205/60R16 (+0.8%); on a 14-inch wheel: 205/70R14 (-0.8%), 215/70R14 (+1.4%). The percentage is the diameter change, which is also your speedometer error.
Can I use 215/60R15 instead of 205/65R15?
Dimensionally yes: 215/60R15 is 1.3% shorter (-9 mm) and 10 mm wider, and at a true 60 mph the speedometer would read 60.8 mph. The extra width needs about 0.20 in of clearance on each side of the tire and a rim width that suits 215 mm.