GarageCalc What 145/70R13 means
145 is the section width in millimeters (5.7 in). 70 is the aspect ratio: the sidewall is 70 percent of the width, so 145 × 0.70 = 102 mm (4.0 in). R is radial construction, and 13 is the wheel diameter in inches (330 mm). Stack two sidewalls on the wheel and you get the overall diameter: 330 + 2 × 102 = 533 mm, or 21.0 in.
A full marking adds a load index and speed rating after the size, for example 145/70R13 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 145/70R13
No common 14-inch size stays within 3 percent of 21.0 in. Going down one size, 145/80R12 is +0.7% with a taller 116 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 145/70R13 tire?
21.0 inches (533 mm) in overall diameter: the 13-inch wheel (330 mm) plus two 102 mm sidewalls. Real tires land within about 1 to 2 percent of that depending on brand, tread depth and pressure.
What is 145/70R13 in inches?
21.0 x 5.7 R13: 21.0 inches tall, 5.7 inches wide, on a 13-inch wheel. The sidewall is 4.0 inches and the circumference is 65.9 inches, so the tire turns 961 times per mile.
What tire sizes are equivalent to 145/70R13?
Within 3 percent of the same diameter on the same 13-inch wheel: 155/65R13 (-0.3%), 165/65R13 (+2.2%), 155/70R13 (+2.6%); on a 12-inch wheel: 145/80R12 (+0.7%), 155/70R12 (-2.1%). The percentage is the diameter change, which is also your speedometer error.
Can I use 155/65R13 instead of 145/70R13?
Dimensionally yes: 155/65R13 is 0.3% shorter (-2 mm) and 10 mm wider, and at a true 60 mph the speedometer would read 60.2 mph. The extra width needs about 0.20 in of clearance on each side of the tire and a rim width that suits 155 mm.