4x4 Low-Range Speed from RPM

Calculate the crawl speed of a 4x4 truck running 1,000 RPM in low-range first gear with 33-inch tires and a 4.56 axle.

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How to use this tool

Enter the engine RPM you want to evaluate.
Enter the overall tire diameter in inches.
Enter the transmission gear ratio for the selected gear and the axle ratio.
The calculator returns vehicle speed in MPH.

In 4-low, trucks move very slowly even at moderate RPM — calculate your exact crawl speed based on your transfer case and gear ratios.

Frequently asked questions

How do you calculate vehicle speed from RPM?: Speed (MPH) = RPM × tire circumference (in) ÷ (gear ratio × axle ratio × 1,056). The constant 1,056 converts inches/minute to MPH (63,360 in/mile ÷ 60 min/hr).
Why does gear ratio matter for speed?: A lower (numerically higher) gear ratio like 3.73 gives more torque but less top speed than a ratio like 2.73 at the same RPM.