Overview
What Is a Tire Size Calculator?
This tool calculates a tire's overall diameter from its size specification (width/aspect ratio/rim diameter) and can compare two sizes.
Compare tire sizes and diameter differences.
This tool calculates a tire's overall diameter from its size specification (width/aspect ratio/rim diameter) and can compare two sizes.
Useful for understanding how a different tire size would affect your vehicle's overall wheel diameter.
Input the standard tire specification numbers.
The overall tire diameter updates automatically.
Format is Width/AspectRatio R RimDiameter - for example, 225/45R17 means 225mm width, 45% aspect ratio, 17-inch rim.
Diameter = Rim Diameter (inches) + 2 × (Width × Aspect Ratio% ÷ 25.4)
Yes, a significantly different overall diameter can cause speedometer and odometer inaccuracy.
Many experts recommend staying within about 3% of your original overall diameter - consult a tire professional for your specific vehicle.
It's the tire's sidewall height as a percentage of its width - lower numbers mean a shorter, wider-looking sidewall.
This depends on your rim width and vehicle clearance - consult a tire professional before changing tire width significantly.
No, this calculates diameter only - other specifications like load and speed ratings are separate considerations.
No, calculations happen entirely in your browser.
Yes, especially for significant size changes, consult a tire professional for proper fitment and safety.
Yes, completely free with no sign-up required.