315/45R21 in inches

How tall is a 315 45R21 tire?

When converted to inches, the equivalent of a 315/45R21 tire size is 32.2x12.4R21. It means that:

  • height overall (or diameter) is 32.2 inches
  • tread width is 12.4 inches
  • wheel diameter is 21 inches

Learn more

315/45R21 tire size in inches
315/45R21 tire size chart

315/45R21 tire size in inches

315/45R21 Height / overall diameter: 32.2 inches
Height / overall diameter
32.2 inches
315/45R21 Tread width: 12.4 inches
Tread width
12.4 inches
315/45R21 Sidewall: 5.6 inches
5.6 inches
315/45R21 Wheel diameter: 21 inches
Wheel diameter
21 inches
315/45R21 Circumference: 101.1 inches
101.1 inches
315/45R21 Revolutions: 626 per mile
626 per mile

315/45R21 — what does it mean?

  • 315 stands for tread width in millimeters
  • 45 is an aspect ration between the tread width and the sidewall in percents
  • R means that the tire has a radial construction
  • 21 is a wheel diameter (or rim) in inches

315/45R21 tire code
315/45R21 tire code

How to convert 315 45R21 to inches?

First of all, we need to divide 315 mm (width) by 25.4 (mm to inch conversion), which will give us a width of 12.4″. Then, 45% of the 12.4″ will result in 5.6″ sidewall.

To get the total height or tire diameter, we need to sum the 21″ rim diameter with two of the sidewall heights. It will result in a 32.2″ total tire diameter (or height).

For your convenience, below is a table for 315/45R21 conversion to inches:

Inches Metric
Overall diameter (height) 32.2″ 818 mm
Tread width 12.4″ 315 mm
Wheel diameter 21″ 818 mm
Sidewall height 5.6″ 142 mm
Circumference 101.1″ 2569 mm
Revolutions 626 / ml 389 / km

Alternatives to a 315/45R21 tire

If you're looking to upsize your 315 45R21 tires, try to stay within 3% deviation of an overall diameter for safety reasons.

Tire Tire diameter Width Wheel Size
275/50R21 31.8″ -0.31% 10.8″ 21″
275/55R21 32.8″ 0.45% 10.8″ 21″
325/40R21 31.2″ -0.81% 12.8″ 21″