Calculate tire RPM from speed and tire size, or find engine RPM, vehicle speed, tire diameter or drive ratio from tire size, gearing and mph or km/h.

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RPM Tire Size Formula

The following formula estimates wheel RPM with speed in mph and tire diameter in inches. Engine RPM additionally includes the selected transmission and axle ratios.

Wheel RPM = Speed ร— 1056 / (pi ร— Tire Diameter) Engine RPM = Wheel RPM ร— Transmission Ratio ร— Axle Ratio

Variables:

  • Wheel RPM is the revolutions per minute of the tire; engine RPM includes the overall drive ratio
  • Speed is the velocity of the vehicle in miles per hour (mph)
  • Tire Diameter is the diameter of the tire in inches

To estimate wheel RPM, multiply speed in mph by 1056 and divide by pi times tire diameter in inches. The familiar factor 336 approximates 1056/pi. Multiply wheel RPM by transmission ratio and axle ratio for engine RPM. These estimates assume no slip; actual rolling circumference differs from nominal tire diameter.

What is RPM in Tires?

RPM, or revolutions per minute, is a measure of how many times a tire completes a full rotation in one minute. It is an important parameter for understanding vehicle dynamics and can affect fuel efficiency, speedometer accuracy, and overall vehicle performance. Tire size can significantly influence RPM; larger tires will have a lower RPM at the same speed compared to smaller tires.

How to Calculate RPM?

The following steps outline how to calculate the RPM of a tire.

  1. First, determine the speed of the vehicle in miles per hour (Speed).
  2. Next, determine the diameter of the tire in inches (Tire Diameter).
  3. Next, use Wheel RPM = Speed * 1056 / (pi * Tire Diameter).
  4. Finally, calculate wheel RPM. For engine RPM, multiply by the selected transmission and axle ratios.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Speed of the vehicle (Speed) = 60 mph

Diameter of the tire (Tire Diameter) = 24 inches