Automobile & Vehicle
Speedometer Gear Calculator
Lets users compare and budget speedometer gear instantly with formula, steps and examples — no manual math.
Enter your details
RPM
in
Your result
Road speed
92.0728 km/h
3000 RPM through 1:1 and 3.9:1 on 25" tires = 92.1 km/h.
In mph
57.2115 mph
Wheel speed
769 RPM
About this calculator
Speed = engine RPM ÷ (gear × final drive) × tire circumference × 60. Use it to check speedometer error after tire or differential changes — a 5% larger tire reads ~5% slow.
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