What Is a Tire Size Calculator and How to Use It

A Tire Size Calculator is a tool that helps you determine the overall diameter, sidewall height, circumference, and revolutions per kilometer of a tire based on its size specifications (width, aspect ratio, and rim diameter). This is especially useful when upgrading or comparing tire sizes for performance, safety, or appearance.

Why Use a Tire Size Calculator?

When replacing tires, it’s important to understand how a new size affects your vehicle’s:

• Speedometer accuracy
• Ride comfort
• Ground clearance
• Fuel economy

Using a tire size calculator takes the guesswork out and gives you accurate measurements instantly.

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How to Use the Tire Size Calculator

Step-by-Step:

1. Enter Tire Width (mm):
   This is the first number on a tire, e.g., 205 in 205/55R16.
2. Enter Aspect Ratio (%):
   This is the second number – the sidewall height as a % of the width. E.g., 55.
3. Enter Rim Diameter (inches):
   This is the last number – e.g., 16 in a 16-inch rim.
4. Click “Calculate Tire Dimensions”
   You’ll get the following results:
   • Sidewall Height in mm
   • Overall Diameter in mm
   • Circumference in mm
   • Revolutions per km (important for speedometer calibration)

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Example:

Input:

• Tire Width: 205
• Aspect Ratio: 55
• Rim Diameter: 16

Results:

• Sidewall Height: 112.75 mm
• Diameter: 631.9 mm
• Circumference: 1984.4 mm
• Revs/km: 504

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FAQ: Tire Size Calculator

Q: What does aspect ratio mean?
A: It’s the height of the tire’s sidewall as a percentage of the tire’s width.

Q: Why do I need revolutions per kilometer?
A: It affects how your speedometer and odometer read speed and distance. Changing tire size can throw these off.

Q: Can I use this to compare two tire sizes?
A: This calculator gives specs for a single tire. Use the values to manually compare two sizes side-by-side.

Q: Does it work for truck or SUV tires?
A: Yes, as long as you input the width, aspect ratio, and rim diameter correctly.

Q: Is this accurate for all tire brands?
A: Yes, dimensions are based on the universal sizing standard. Slight variations may occur between brands.