Gear Ratio RPM Calculator - Output Speed from Gear Ratios

Calculate output RPM from input speed and gear ratios.

Essential for mechanical engineering, automotive, and transmission design.

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How This Tool Works

This calculator finds output shaft speed from an input RPM and one or two gear stages. For each stage, it defines the gear ratio as Driven Gear Teeth / Driver Gear Teeth. The total gear ratio is the product of all stage ratios.

The output speed is calculated as Output RPM = Input RPM / Total Gear Ratio. For example, a 20-tooth driver gear turning a 60-tooth driven gear has a 3:1 ratio, so a 1,800 RPM input produces a 600 RPM output.

Why This Matters

Gear ratio calculations help predict speed reduction, overdrive, torque multiplication, and rotation direction in mechanical systems. A ratio above 1 reduces speed and increases torque, while a ratio below 1 increases output speed and reduces torque.

  • Single stage: Use the driven gear teeth divided by the driver gear teeth.
  • Two stage: Multiply the two stage ratios before dividing the input RPM.
  • Direction: Each meshed gear pair reverses rotation, so an odd number of stages reverses direction and an even number returns it to the same direction.

Frequently Asked Questions

Common questions about the Gear Ratio RPM Calculator - Output Speed from Gear Ratios

Angular velocity measures how fast something rotates, expressed as angle change per unit time. Common units include radians per second (rad/s), degrees per second, and revolutions per minute (RPM).
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Sources & References

International System of Units (SI): angular velocity

Angular velocity is measured in the radian per second (rad/s). Conversions between SI and other units use exact, internationally agreed factors maintained by NIST.
→Source: NIST — International System of Units (SI)

International System of Units (SI)

Authoritative definitions for angular velocity, from the BIPM SI Brochure (9th edition), the defining reference for the SI.
→Source: BIPM — SI Brochure (9th ed.)

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