Tire Size Calculator - Tire Size Meaning
Decode tire size markings and understand what each number means with this free online tire size calculator.
Enter tire size: 225/60R16 → Width: 225, Ratio: 60, Rim: 16
About Tire Size Calculation
Tire size markings on the sidewall of every tire contain vital information about the tire's dimensions, construction, and performance capabilities. Understanding these markings is essential for selecting replacement tires, upgrading wheel sizes, and ensuring proper vehicle performance. The most common tire size format is P-metric, which uses a standardized system adopted globally.
A typical tire size like P225/45R17 91H breaks down as follows: P indicates the tire is designed for passenger vehicles, 225 is the section width in millimeters, 45 is the aspect ratio (sidewall height as a percentage of width), R denotes radial construction, 17 is the wheel diameter in inches, 91 is the load index, and H is the speed rating. Each component affects how the tire performs, fits, and handles on your vehicle.
When selecting replacement tires, it is important to understand equivalency between different sizing systems. P-metric (US), Euro-metric, and LT-metric (light truck) tires may have different markings but can be interchangeable in certain size ranges. Our tire size calculator helps you decode any tire marking, find equivalent sizes across different systems, and understand the performance implications of changing tire sizes on your vehicle.
How to Use the Tire Size Calculator
Enter the complete tire size from your tire sidewall, such as 225/45R17 or P215/65R15. The calculator will decode every component, displaying the width, aspect ratio, construction type, wheel diameter, overall diameter, sidewall height, and circumference in both imperial and metric units.
To find equivalent tire sizes, enter your current size and the calculator will show compatible alternatives. You can explore options with different widths, aspect ratios, or wheel diameters while maintaining the overall diameter within acceptable tolerance. This is useful when upgrading wheels or finding the best available tire size.
The calculator also displays the load index and speed rating decode, showing the maximum load capacity and speed rating for your tires. Use this information to ensure replacement tires meet or exceed your vehicle manufacturer's requirements for safe operation.
Frequently Asked Questions
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