GarageCalc What 305/45R22 means
305 is the section width in millimeters (12.0 in). 45 is the aspect ratio: the sidewall is 45 percent of the width, so 305 × 0.45 = 137 mm (5.4 in). R is radial construction, and 22 is the wheel diameter in inches (559 mm). Stack two sidewalls on the wheel and you get the overall diameter: 559 + 2 × 137 = 833 mm, or 32.8 in.
A full marking adds a load index and speed rating after the size, for example 305/45R22 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 305/45R22
No common size on a 21 or 23-inch wheel stays within 3 percent of 32.8 in, so 305/45R22 is best replaced like for like. The comparison calculator checks any candidate against the 3 percent guideline.
Frequently asked questions
How tall is a 305/45R22 tire?
32.8 inches (833 mm) in overall diameter: the 22-inch wheel (559 mm) plus two 137 mm sidewalls. Real tires land within about 1 to 2 percent of that depending on brand, tread depth and pressure.
What is 305/45R22 in inches?
32.8 x 12.0 R22: 32.8 inches tall, 12.0 inches wide, on a 22-inch wheel. The sidewall is 5.4 inches and the circumference is 103.1 inches, so the tire turns 615 times per mile.
What tire sizes are equivalent to 305/45R22?
Within 3 percent of the same diameter on the same 22-inch wheel: 285/45R22 (-2.2%). The percentage is the diameter change, which is also your speedometer error.