Physics

Transmission Calculator

Find vehicle speed from engine rpm, gearing and tire size.

Engine RPM (rpm)

Gear ratio (:1)

Final drive ratio (:1)

Tire diameter

Calculated Output

Speed 62.716

Speed 100.93

Formula: speed = rpm·π·tire·60 ÷ (gear·final·63360)

Step-by-Step Breakdown

1. Values used:

2. Engine RPM = 3,000 rpm

3. Gear ratio = 1 :1

4. Final drive ratio = 3.7 :1

5. Tire diameter = 26

7. Speed = 62.716

8. Speed = 100.93

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The math behind it

Wheel rpm = engine rpm ÷ (gear × final). Multiply by tire circumference to get distance per minute, then convert to speed.

3000 rpm, 1:1 gear, 3.7 final, 26" tire → about 65 mph.

Why do taller tires raise speed?

They travel farther per revolution, lowering rpm at a given speed.