An object’s rotational speed, measured in rotations per minute (RPM), can be converted to a linear speed, miles per hour, by considering the diameter of the circle the object spins around. The bigger the diameter of the circle, the bigger the circumference.
How to calculate the circumference
You need to multiply the diameter in inches by pi, which is approximately 3.14. For example, if a tire is two inches in diameter, then its circumference is 9.42 feet: 3 x 3.14 = 9.42 inches.
Using our official app, you can calculate the results offline. The app also offers several other calculators.
MPH to RPM Formula
Simple formula: convert miles per hour into inches per minute. One mile has 63360 inches and one hour has 60 minutes. Let’s say 152 miles per hour (MPH) and the diameter is 36.4.
152 ÷ 60 = 2.5333 miles per minute
2.5333 * 63360 = 160509.888 inches per minute
Time to calculate the circumference, which we already know is: = diameter * pi
36.4 * 3.14159= 114.353876 circumference (in)
Now simply divide it with circumference value.
RPM = 160509.888 ÷ 114.353876 = 1403.643
MPH to RPM Calculator
You can use our online MPH to RPM calculator to convert miles per hour to revolutions per minute.
Get to know about miles per gallon using the Miles per Gallon Calculator.
