Tire-Size-Calculator

Tire Size Calculator

Compare tire sizes, convert metric tire sizes to inches, calculate overall diameter, circumference, sidewall height, revolutions per mile, and see how a tire size change can affect speedometer reading.

Metric Tire Size

Example: 275/60R20. Enter section width, aspect ratio, and wheel diameter.

Standard Tire Size

Example: 35x13.50R20. Enter diameter, width, and wheel diameter.

Tire Size Comparison

Compare current tire size to a new tire size. This is useful when changing tire height, wheel size, or looking at how much speedometer reading may change.

Current Tire

New Tire

Quick Tire Conversion

Convert millimeters to inches, inches to millimeters, diameter to circumference, and circumference to adjusted revs per mile.

Tire Height Lookup

Select a common tire height to see circumference and revolutions per mile.

How to Read Tire Size

A metric tire size like 275/60R20 breaks down like this:

  • 275 is the tire width in millimeters.
  • 60 is the aspect ratio. The sidewall is 60% of the tire width.
  • R20 means radial construction for a 20 inch wheel.

Common Tire Size Searches This Calculator Helps With

  • Metric tire size to inches
  • Tire diameter calculator
  • Tire height calculator
  • Tire circumference calculator
  • Revolutions per mile calculator
  • Adjusted revolutions per mile for speedometer correction
  • Speedometer difference after tire size change
  • Compare 275/60R20 vs 285/65R20
  • Convert tire width from mm to inches
  • Find tire size close to 33 inch, 34 inch, 35 inch, or 37 inch tires

Why Tire Size Matters

Tire diameter changes affect more than just appearance. A taller tire travels farther per revolution, which can make the speedometer read lower than actual road speed. Tire size can also affect gearing, shift behavior, acceleration, towing feel, and traction control behavior.

Note: This calculator gives mathematical tire size estimates. Actual mounted height can vary by tire brand, tread design, load rating, wheel width, air pressure, vehicle weight, and tire construction. The adjusted revs per mile number uses an estimated real-world rolling factor to better approximate loaded tire radius for speedometer correction.