315/30R21 in inches

How tall is a 315 30R21 tire?

When converted to inches, the equivalent of a 315/30R21 tire size is 28.4x12.4R21. It means that:

  • height overall (or diameter) is 28.4 inches
  • tread width is 12.4 inches
  • wheel diameter is 21 inches

Learn more

315/30R21 tire size in inches
315/30R21 tire size chart

315/30R21 tire size in inches

315/30R21 Height / overall diameter: 28.4 inches
Height / overall diameter
28.4 inches
315/30R21 Tread width: 12.4 inches
Tread width
12.4 inches
315/30R21 Sidewall: 3.7 inches
Sidewall
3.7 inches
315/30R21 Wheel diameter: 21 inches
Wheel diameter
21 inches
315/30R21 Circumference: 89.2 inches
Circumference
89.2 inches
315/30R21 Revolutions: 711 per mile
Revolutions
711 per mile

315/30R21 — what does it mean?

  • 315 stands for tread width in millimeters
  • 30 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

315/30R21 tire code
315/30R21 tire code

How to convert 315 30R21 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, 30% of the 12.4″ will result in 3.7″ 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 28.4″ total tire diameter (or height).

For your convenience, below is a table for 315/30R21 conversion to inches:

Inches Metric
Overall diameter (height) 28.4″ 721 mm
Tread width 12.4″ 315 mm
Wheel diameter 21″ 721 mm
Sidewall height 3.7″ 95 mm
Circumference 89.2″ 2264 mm
Revolutions 711 / ml 442 / km

Alternatives to a 315/30R21 tire

If you're looking to upsize your 315 30R21 tires, try to stay within 3% deviation of an overall diameter for safety reasons.

Tire Tire diameter Width Wheel Size
245/35R21 27.8″ -0.53% 9.6″ 21″
245/40R21 28.8″ 0.38% 9.6″ 21″
255/35R21 28″ -0.35% 10″ 21″
255/40R21 29″ 0.55% 10″ 21″
265/35R21 28.4″ 0% 10.4″ 21″
275/35R21 28.6″ 0.17% 10.8″ 21″
285/30R21 27.8″ -0.53% 11.2″ 21″
285/35R21 28.8″ 0.38% 11.2″ 21″
295/30R21 28″ -0.35% 11.6″ 21″
295/35R21 29.2″ 0.72% 11.6″ 21″