GarageCalc What 205/45R16 means
205 is the section width in millimeters (8.1 in). 45 is the aspect ratio: the sidewall is 45 percent of the width, so 205 × 0.45 = 92 mm (3.6 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 × 92 = 591 mm, or 23.3 in.
A full marking adds a load index and speed rating after the size, for example 205/45R16 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 205/45R16
Going up one wheel size, the closest match is 205/40R17 at +0.8% diameter with a 82 mm sidewall instead of 92 mm. Going down one size, 195/55R15 is +0.8% with a taller 107 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 205/45R16 tire?
23.3 inches (591 mm) in overall diameter: the 16-inch wheel (406 mm) plus two 92 mm sidewalls. Real tires land within about 1 to 2 percent of that depending on brand, tread depth and pressure.
What is 205/45R16 in inches?
23.3 x 8.1 R16: 23.3 inches tall, 8.1 inches wide, on a 16-inch wheel. The sidewall is 3.6 inches and the circumference is 73.1 inches, so the tire turns 867 times per mile.
What tire sizes are equivalent to 205/45R16?
Within 3 percent of the same diameter on the same 16-inch wheel: 185/50R16 (+0.1%), 195/45R16 (-1.5%), 195/50R16 (+1.8%); on a 17-inch wheel: 205/40R17 (+0.8%), 215/40R17 (+2.2%); on a 15-inch wheel: 195/55R15 (+0.8%), 205/50R15 (-0.8%). The percentage is the diameter change, which is also your speedometer error.