Gear Ratio Calculator

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Gear ratio, output rpm and output torque (with efficiency) from the tooth counts — one gear pair or a two-stage compound train

This tool runs entirely in your browser — no file or data is sent to any server.

Enter the values

What to work out

Driver gear teeth (T₁)

Driven gear teeth (T₂)

Input speed

Input torque (0 to skip)

Gear train efficiency (η)

100 for an ideal (lossless) train

Result

Gear ratio

Output speed

480rpm

Output torque

30N·m

An idler gear between them does not change the ratio, only the direction. Direction here assumes external spur gears.

Working

Formulas

Assumptions

Properly meshed gears with no slip; in the compound train T₂ and T₃ share one shaft.
Efficiency 100% means an ideal (lossless) train — in practice the output torque is somewhat lower.

Sources: R. S. Khurmi & J. K. Gupta, Theory of Machines · S. S. Rattan, Theory of Machines

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