Tire Size Conversion Calculator

Convert a tire size from metric to inches by entering the size below. Or, select the option to convert a tire size from inches to metric.

Convert Metric to Inches

Tire Size
/ R

Convert Inches to Metric

Tire Size
x R

Converted Tire Size:

Learn how we calculated this below

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How to Convert a Tire Size From Metric to Inches

Converting a tire size measured using metric notation to its equivalent size in inches (also known as Imperial or SAE notation) can be done using a few formulas.

A tire’s metric size is composed of the section width in millimeters, the aspect ratio, and the rim diameter in inches. A tire’s inch size is made up of the tire diameter in inches, the section diameter in inches, and the rim diameter in inches.

Icon of a wheel with tire and rim

To convert tire sizes from metric to inch sizes, follow these easy steps:

First, we need to convert the section width from millimeters to inches. This can be done by dividing the number by 25.4. You can also use our millimeters to inches conversion calculator.

Next, we need to find the tire diameter in inches. You can use our tire size calculator to find the tire size, or you can use a few formulas.

sidewall height = section width × (aspect ratio ÷ 100)
tire diameter = (sidewall height × 2) + rim diameter

Thus, the wheel diameter in inches is equal to the sidewall height (calculated by taking the section width in inches multiplied by the result of the aspect ratio divided by one hundred) multiplied by two and added to the rim diameter.

To finish the conversion, let’s put it all together by composing the new size as the diameter “X” section width “R” rim diameter.

For example, let’s convert a 225/60R16 metric tire size to its equivalent size in inches:

section width = 225 ÷ 25.4
section width = 8.86″

sidewall height = 8.86″ × (60 ÷ 100)
sidewall height = 8.86″ × 0.6
sidewall height = 5.316″

diameter = (5.316″ × 2) + 16″
diameter = 10.632″ + 16″
diameter = 26.632″

Putting it together, the tire’s inch size is 26.632 X 8.86 R 16.

How to Convert a Tire Size From Inches to Metric

To convert a tire size from inches to metric, the steps above simply need to be reversed.

Start by converting the section width from inches to millimeters by multiplying by 25.4. You can also use an inches to millimeters conversion calculator.

Then, solve the aspect ratio using the following formulas:

sidewall height = (tire diameter – rim diameter) ÷ 2
aspect ratio = sidewall height ÷ section width × 100

So, the aspect ratio is equal to the tire diameter minus the rim diameter, divided by two, which is then divided by the section width and multiplied by 100.

The metric tire size is stated as the section width “/” aspect ratio “R” rim diameter.

For example, let’s convert a 26.63X8.86R16 inch tire size to metric.

section width = 8.86″ × 25.4
section width = 225 mm

sidewall height = (26.63″ – 16″) ÷ 2
sidewall height = 10.63″ ÷ 2
sidewall height = 5.315″

aspect ratio = 5.315″ ÷ 8.86″ × 100
aspect ratio = 60

So, the metric tire size is 225 / 60 R 16.