GarageCalc What 295/45R20 means
295 is the section width in millimeters (11.6 in). 45 is the aspect ratio: the sidewall is 45 percent of the width, so 295 × 0.45 = 133 mm (5.2 in). R is radial construction, and 20 is the wheel diameter in inches (508 mm). Stack two sidewalls on the wheel and you get the overall diameter: 508 + 2 × 133 = 774 mm, or 30.5 in.
A full marking adds a load index and speed rating after the size, for example 295/45R20 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 295/45R20
Going up one wheel size, the closest match is 295/40R21 at -0.5% diameter with a 118 mm sidewall instead of 133 mm. Going down one size, 275/55R19 is +1.5% with a taller 151 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 295/45R20 tire?
30.5 inches (774 mm) in overall diameter: the 20-inch wheel (508 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 295/45R20 in inches?
30.5 x 11.6 R20: 30.5 inches tall, 11.6 inches wide, on a 20-inch wheel. The sidewall is 5.2 inches and the circumference is 95.7 inches, so the tire turns 662 times per mile.
What tire sizes are equivalent to 295/45R20?
Within 3 percent of the same diameter on the same 20-inch wheel: 285/45R20 (-1.2%), 275/50R20 (+1.2%), 275/45R20 (-2.3%); on a 21-inch wheel: 295/40R21 (-0.5%), 275/45R21 (+1.0%); on a 19-inch wheel: 275/55R19 (+1.5%), 275/50R19 (-2.1%). The percentage is the diameter change, which is also your speedometer error.