Tire Size Conversion Calculator: Convert Between Metric and Inches

Convert Tire Sizes

How to Convert Tire Sizes

Converting tire sizes between metric and inches is essential for comparing different tire options and ensuring proper fitment. This calculator helps you convert between the two systems quickly and accurately.

Tire Size Conversion Formulas

The following formulas are used in our tire size conversion calculations:

Section Width (inches to mm): $W i d t h_{m m} = W i d t h_{i n c h e s} \times 25.4$
Section Width (mm to inches): $W i d t h_{i n c h e s} = \frac{W i d t h_{m m}}{25.4}$
Sidewall Height (inches): $S i d e w a l l_{i n c h e s} = \frac{W i d t h_{m m} \times A s p e c t R a t i o}{2540}$
Overall Diameter (inches): $D i a m e t e r_{i n c h e s} = R i m D i a m e t e r + (2 \times S i d e w a l l_{i n c h e s})$
Aspect Ratio (%): $A s p e c t R a t i o = \frac{S i d e w a l l_{i n c h e s}}{W i d t h_{i n c h e s}} \times 100$

Calculation Steps

Metric to Inches Conversion:

Convert section width from millimeters to inches
Calculate sidewall height in inches using the aspect ratio
Calculate overall diameter by adding rim diameter and twice the sidewall height

Inches to Metric Conversion:

Convert section width from inches to millimeters
Calculate sidewall height in inches from overall diameter and rim diameter
Calculate aspect ratio using sidewall height and section width

Example Calculation

Let's convert a metric tire size 225/45R17 to inches:

Convert section width to inches: $W i d t h_{i n c h e s} = \frac{225}{25.4} = 8.86 inches$
Calculate sidewall height: $S i d e w a l l_{i n c h e s} = \frac{225 \times 45}{2540} = 3.98 inches$
Calculate overall diameter: $D i a m e t e r_{i n c h e s} = 17 + (2 \times 3.98) = 24.96 inches$

The equivalent size in inches is approximately 24.96 x 8.86 R17.

Tire Size Conversion Diagram

This diagram visually represents the dimensions of the converted tire size. It helps to easily compare the section width, sidewall height, rim diameter, and overall diameter of the tire.

Tire Size Conversion Calculator