Tire Size Calculator
Enter your tire size markings and get the sidewall height, overall diameter, circumference and revolutions per kilometre. Optionally compare against a reference size to see how they differ.
How it works
Sidewall height = width × aspect ÷ 100. Overall diameter = rim diameter + 2 × sidewall height (converted). Circumference = π × diameter. A diameter difference above 3% from the original size is generally not recommended for safety and speedometer accuracy.
Frequently asked questions
What does 205/55 R16 mean?
205 is the section width in millimetres, 55 is the aspect ratio (sidewall height is 55% of the width), and R16 is the rim diameter in inches.
How close must a new size match the original?
Keep the overall diameter within about 3% of the original. Larger differences affect speedometer accuracy, ABS/ESP behaviour and can cause rubbing.