How to Find Rpm
- 1). Multiply the object's speed in miles per hour by 88.2 to convert it to feet per minute. For instance, if an object moves at 70 mph: 70 --- 88.2 = 6,174 ft/min
- 2). Multiply the object's radius by 6.283, which is twice the constant pi. For instance, if a vehicle's wheels have radius of 0.75 feet: 0.75 --- 6.283 = 4.71. This is the object's circumference, measured in feet.
- 3). Divide the object's linear speed by its circumference: 6,174 ÷ 4.71 = 1,311. This is the object's rotation speed, measured in RPM.