RPM Calculator
Calculate engine RPM from vehicle speed, tire size, and gear ratios, or solve for any variable.
How It Works
Enter vehicle speed, tire diameter, transmission gear ratio, and axle ratio. The calculator solves for engine RPM, or you can enter RPM to find vehicle speed.
Formula
RPM = Speed (mph) x Gear Ratio x Final Drive x 336 / Tire Diameter
Frequently Asked Questions
Why does RPM matter?
RPM (revolutions per minute) tells you where in the power band an engine is operating. Peak horsepower and torque occur at specific RPM ranges, so knowing your operating RPM helps optimize gear selection.
What is a good highway cruising RPM?
Most fuel-efficient highway cruising is between 1500-2500 RPM for most vehicles. Higher RPM means the engine is working harder and using more fuel.