Tire Size Calculator

Tire size is calculated using the tire code format (e.g., 225/60R16). The first number is width in mm, the second is aspect ratio (sidewall height as percentage of width), and the third is rim diameter in inches. Tire diameter = rim diameter + (2 × sidewall height).

The tire code contains three key measurements: width in millimeters, aspect ratio as a percentage, and rim diameter in inches. For example, in 225/60R16, 225mm is the width, 60% is the aspect ratio, and 16 inches is the rim diameter.

Larger tires will cause your speedometer to read slower than actual speed, while smaller tires make it read faster. A 3% change in tire diameter typically results in a 3% speedometer error, which can affect odometer readings and fuel economy calculations.

Consider speedometer accuracy, ground clearance, wheel well space, load capacity, and vehicle handling. Maintaining the same overall diameter helps preserve speedometer accuracy and vehicle dynamics while allowing for different wheel and tire combinations.

Sidewall height equals tire width multiplied by aspect ratio. For a 225/60R16 tire: 225mm × 0.60 = 135mm sidewall height. Convert to inches by dividing by 25.4 (135mm ÷ 25.4 = 5.31 inches).

Tire circumference determines how far your vehicle travels with each wheel rotation. It's calculated as π × tire diameter and is used to determine revolutions per mile, which affects speedometer calibration and odometer accuracy.

You can use different tire sizes as long as they maintain similar overall diameter, fit in the wheel wells, and meet load requirements. Plus sizing (larger wheels with lower profile tires) is common for improved handling and appearance.

Most passenger car tires make 750-850 revolutions per mile, depending on size. Smaller tires have more revolutions per mile, while larger tires have fewer. This number is calculated as 5,280 feet (1 mile) divided by tire circumference in feet.