Calculate RPM for Given Speed(MPH), Rear Gear Ratio, and Trans Gear Ratio

With our RPM calculator, you can calculate your engine's RPM based off of your vehicle's speed, tire diameter, rear gear ratio, and transmission gear ratio. Keep in mind that our calculator does NOT take into account drive train loss, road and weather conditions, or the skill of the driver.

Engine RPM, or revolutions per minute, is defined as the number of times the crankshaft of your engine rotates within the span of one minute. Your vehicle's RPM can be calculated at any speed as long as you give the tire size, axle ratio, and final transmission gear ratio. Using this calculation, you can match oversized tires with new ring and pinion gears to get the engine RPM at highway speed you desire.