Tire Size Calculator calculates overall tire diameter, circumference, revolutions per mile/km and sidewall height, from the tire size designation on a tire.

This calculator also gives the option to compare tires. e.g., It compares the tire circumference and the overall tire diameter of one or more additional tires with the base tire and gives an information about the tire upsizing/downsizing: does the new tire exceeds the recommended upper or lower limit for the tire upsizing/downsizing. Also it shows the amount of speedometer error due to changing the tire diameter/circumference.

 

At the bottom of the page there are detailed instructions how to use this calculator and about the tire size designation.

Tire Size Calculator

Tire Size Calculator

select tire size

eg. 195/65R15

 / R

NOTICE: Tire comparison - To do tire comparison, select another tire size and click the "Calculate Tire Dimensions" button again, so you could compare just selected tire size with the first one, selected and calculated(base tire, that should be the OE Tire). After that, click on the "Compare this tire" button. The comparison results are positioned lower down on the page. The comparison is always made against the first selected and calculated tire size(the base tire).

Tire Dimensions

Tire Size-
mminches
Tire
Width
--
Aspect
Ratio
--
Rim
Diameter
--
Sidewall
Height
--
Tire
Diameter
--
Circum-
ference
--
Revolutions--

This button will be available for use after you select another tire size, besides the first one selected and calculated, and click on the "Calculate…" button again.

Click on this button to compare just selected and calculated tire size with the base tire(first selected and calculated tire size), which iz the basis for the tire comparison. See the comparison results in the "Tire Comparison" section below.

Tire Comparison

Measurement units

For the specific tire size, the table column named "diff" contains, in its rows, differences between the speciic tire size and the base tire size measurements.

Base tire
Tire Size-
mmdiff
Tire
Width
--
Aspect
Ratio
--
Rim
Diameter
--
Sidewall
Height
--
Tire
Diameter
--
Circum-
ference
--
Revolutions--
-

To start new comparison of another set of tires with the Base tire(first entered tire), click on the button "Clear Compared Tires" and enter new tire size into the calculator.

To start completely over, with the new tire size for the Base tire(the tire size entered first) - please click on the button "Refresh Page-Restart Calc" or refresh the page in your browser.

A negligible error can arise due to rounding off numbers.

Disclaimer:
The calculator results are for informative purposes only. The tyresizecalculator.com is not responsible for any miscalculations of this calculator or any other errors that may arise with its usage.

Try out our other calculators:

  • Find out which tire dimensions are adequate for your new wheels with Plus Sizing Calculator.
  • Check the speedometer for the speedo error which may arise from the tire size change, for any speedometer reading.
  • Find out which wheel size is suitable for your new tires.
  • What is the best tire size for your rim? Tire Size for Rim Size/Width Calculator.
  • Find the wheel offset and the wheel backspace, the important measurements for positioning the wheel/tire assembly inside the wheel well.
  • The tire size converter will convert the inch tire size to the metric tire size and the other way around. The converter also displays adequate real tires with the dimensions which are closest to the calculated tire size, if such exist.

Related articles:

The Tire Size Designation

The tire size designation is consisted of the following elements:

[Tire Width]/[Aspect Ratio]R[Rim Diameter]

For example tire size 195/65R15 has:

Tire Width = 195 mm

Aspect Ratio = 65%

Aspect Ratio is the sidewall height as a percentage of the section width. For example, sidewall height of this tire will be 195 x 0.65 = 126.75 mm

Tire type = R - Radial-ply structure

Rim Diameter = 15 inches

How to use the Tire Size Calculator and how to compare the tire dimensions

To get the tire dimensions for a tire, first select the tire size, then click on the "Calculate Tire Dimensions" button. Dimensions for the selected tire size will be presented in the table below the calculator.

Compare tire dimensions

The first selected/entered tire size in the Tire Size Calculator is the Base tire, as the base for a comparision with other tires.

You have an option to compare two additional tire sizes to the base tire size. To use this option, after you've got dimensions for the first selected tire size - the base tire, select another tire size and click again on the "Calculate Tire Dimensions" button in order to get dimensions for that tire size.

After that, the "Compare this tire" button will be enabled and you can click on it to add the last calculated tire size dimensions for a comparision with the base tire size. Results of the comparision are presented in the section "Tire Comparison".

Every compared tire, with its dimensions, is contained in a section called "Compared Tire x" and it has the table column "Diff" which shows calculated differences between the compared tire dimensions and the base tire dimensions.

At the bottom of the section "Tire Comparison" there is the "Clear compared tires" button which, when clicked, clears all tires selected for the comparison, and you can start over, to add new tire sizes you want to compare with the existing base tire.

If you want to change the base tire, which is the basis for the comparison with other selected tires, refresh this page by clicking on the "Refresh Page-RestartCalc" button in the section "Tire Comparison" or click on the Refresh page button in your browser.