Tire Size Calculator
Compare tire sizes and calculate diameter, width, and sidewall height.
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Tire Size Calculator
Enter tire size (e.g., 225/45R18)
Tire Size Calculator
A tire size calculator converts between different tire size formats and calculates the overall diameter, sidewall height, and circumference of a tire. Understanding tire dimensions helps when comparing replacement options, calculating speedometer accuracy, and selecting appropriate wheel/tire combinations.
Common Uses
- Converting tire sizes when considering replacement options
- Checking speedometer accuracy after changing tire sizes
- Comparing overall diameter of different tire sizes
- Planning lifted truck or lowered vehicle fitments
Frequently Asked Questions
How do I read a tire size like 225/55R17?
225 = section width in mm (tire width). 55 = aspect ratio (sidewall height is 55% of width). R = radial construction. 17 = wheel diameter in inches. So: 225mm wide, sidewall height = 225 × 0.55 = 123.75mm, fits a 17-inch wheel.
How does tire size affect speedometer?
A larger diameter tire travels more distance per revolution, making your speedometer read slower than actual speed. A smaller tire does the opposite. A 3% larger tire means your speedometer shows 60 mph when you're actually going 61.8 mph.
Is this calculator free to use?
Yes. All calculators on zenicalculator.com are completely free with no registration required.
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