What is the output RPM for a 10:1 reduction?

By FieldCalc operator · October 13, 2026

Learn the reduction-ratio definition, calculate output RPM, combine simple gear stages and work backwards from a target speed.

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Define the ratio first

Here, reduction ratio i means input speed divided by output speed. A ratio of 10 means ten input revolutions for one output revolution. The ratio is dimensionless; RPM counts revolutions per minute. Manufacturers can write ratios in different orders, so check the specification rather than relying on the notation alone.

Calculate output speed

Output RPM = input RPM ÷ reduction ratio. With 1,400 RPM input and a ratio of 10, output speed is 140 RPM. If input speed changes to 1,750 RPM, output becomes 175 RPM with the same gearbox. Use input speed for the operating condition you are examining.

Compare ratios

At 1,400 RPM input, ratios of 5, 10 and 20 give 280, 140 and 70 RPM respectively. Doubling the reduction ratio halves output speed. This describes shaft rotation, not directly conveyor travel speed or machine production rate.

Work backwards from a target

For a 70 RPM target with 1,400 RPM input, the required ratio is 1,400 ÷ 70 = 20. Available gearboxes may use standard ratios. Check the acceptable speed range, rated input speed and permissible output torque before selecting a product.

Combine simple gear stages

An 18-tooth driver turning a 54-tooth driven gear gives a ratio of 3. A second 4:1 reduction gives an overall ratio of 3 × 4 = 12. At 1,440 RPM input, output is 120 RPM. This approach applies to simple independently defined stages; planetary gear arrangements need their own kinematic relationship.

Convert shaft RPM to travel speed

A 100 mm diameter roller directly connected to a 140 RPM shaft has theoretical surface speed π × 0.1 × 140 ≈ 43.98 m/min, assuming no slip. Equal shaft speeds do not imply equal travel speeds when roller diameters differ. Use effective roller diameter and account for slip.

Check torque and operating limits

Ideal output torque is input torque multiplied by reduction ratio. Real transmitted torque also depends on efficiency and must remain within gearbox ratings. Do not multiply RPM by efficiency as a shortcut. Inverter settings and induction-motor load can change actual input speed, so recalculate using the relevant operating RPM.

A guide to preliminary calculations. Check manufacturer specifications and operating conditions before applying results.