GarageCalc What 205/50R15 means
205 is the section width in millimeters (8.1 in). 50 is the aspect ratio: the sidewall is 50 percent of the width, so 205 × 0.50 = 103 mm (4.0 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 × 103 = 586 mm, or 23.1 in.
A full marking adds a load index and speed rating after the size, for example 205/50R15 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 205/50R15
Going up one wheel size, the closest match is 195/45R16 at -0.7% diameter with a 88 mm sidewall instead of 103 mm. Going down one size, 195/60R14 is +0.6% with a taller 117 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 205/50R15 tire?
23.1 inches (586 mm) in overall diameter: the 15-inch wheel (381 mm) plus two 103 mm sidewalls. Real tires land within about 1 to 2 percent of that depending on brand, tread depth and pressure.
What is 205/50R15 in inches?
23.1 x 8.1 R15: 23.1 inches tall, 8.1 inches wide, on a 15-inch wheel. The sidewall is 4.0 inches and the circumference is 72.5 inches, so the tire turns 874 times per mile.
What tire sizes are equivalent to 205/50R15?
Within 3 percent of the same diameter on the same 15-inch wheel: 185/55R15 (-0.3%), 195/55R15 (+1.6%), 195/50R15 (-1.7%); on a 16-inch wheel: 195/45R16 (-0.7%), 205/45R16 (+0.8%); on a 14-inch wheel: 195/60R14 (+0.6%), 185/60R14 (-1.4%). The percentage is the diameter change, which is also your speedometer error.