Tire/Wheel size calculator
Tire Size Calculator calculates tire diameter, circumference, revolutions per mile/km from the tire size designation on a tire.
This calculator also gives the option to compare tires. e.g., It compares the circumference and the outer diameter of one or more additional tires to the base tire and gives an information about upsizing/downsizing: does the new tire exceeds the recommended upper or lower limit for upsizing/downsizing. Also it shows the amount of speedo error due to changing the tire diameter/circumference.