TIRE SIZE INFO
Written by: Jeff Bakke (Walking Eagle)

To use the tire calculator, your Internet browser must support JavaScript.  

Many tire sizes are printed in inches either on the tire itself or in advertising.  Yet, many common tire sizes are not provided in inches, they are printed for example as 285/75/16.  This makes it hard to compare tire sizes when shopping for your new tires.  This tire calculator is designed to translate metric tire sizes into inches. 

To use this program you need three pieces of information. The tire width, aspect ratio, and wheel diameter.

The following are the three easy steps on using the tire calculator.  We will use a tire size of  285/75/16 as the example tire size. 

  1. Enter the 1st number in the box to the right of Tire Width.  The 1st number represents the tread width measured in millimeters.  In the above example the number is 285.
  2. Enter the 2nd number in the box to the right of Aspect Ratio.  The 2nd number represents the aspect ratio of the sidewall versus the tread width displayed as a percentage.  In the above example, the number is 75.
  3. Enter the 3rd number in the box to the right of Wheel Diameter.  The 3rd number represents your wheel size.  This number is 16 in the above example.

 The tire calculator will the calculate tire height and width for you in inches.  Below the tire calculator is an example using the formulas to hand calculate the conversion from metric to inches.

Step 1: Key in the Metric Tire Size information.

Metric Tire Size

Step 2: To convert the tire size, click on the "Convert Tire Size" button.

Converted Tire Size

Tire Width:

Aspect Ratio:

Tire Width (inches):

Wheel Diameter:

Tire Height (inches):

Step 2: To convert the tire size, click on the "Convert Tire Size" button. 

To run program again, reenter information in Metric Tire Size box and click on "Convert Tire Size" button once again to update the Converted Tire Size information.

 

Here is the example doing by hand for a tire size of 285/75/16.

 

  1. The tire height is determined by using this formula:

((Tread Width * (Aspect Ratio / 100) * 2) * 0.0393700787402) + Wheel Size

Or

Using the above tire size of 285/75/16:

((285 * (75 / 100) * 2) * 0.0393700787402) + 16

= 32.83 for the height

 

  1. The tire width is determined by using this formula:

 

Tread Width * 0.0393700787402

Or

Using the above tire size of 285/75/16:

285 * 0.0393700787402

= 11.22