Motor Speed Calculator - Free Online Tool

Calculate your motor speed with our free online tool.

Get accurate results instantly.

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How This Tool Works

This calculator finds AC motor speed from supply frequency and the number of motor poles. It uses the synchronous speed formula Ns = 120f / P, where f is frequency in hertz and P is the number of poles.

For induction motors, it also applies slip to estimate loaded shaft speed: N = Ns x (1 - s), where s is slip as a decimal. For example, a 60 Hz, 4-pole induction motor with 3% slip has a synchronous speed of 1,800 RPM and an estimated actual speed of 1,746 RPM.

Why This Matters

Motor speed affects pulley ratios, fan and pump performance, machine timing, and equipment selection.

Checking frequency, pole count, and slip helps distinguish the ideal rotating field speed from the real shaft speed under load.

Common Mistakes to Avoid

  • Do not ignore pole count: More poles mean lower synchronous RPM at the same frequency.
  • Do not apply slip to synchronous motors: Synchronous motors run at the rotating field speed under normal locked operation.
  • Enter slip as a percent: Use 3 for 3% slip, not 0.03.

Frequently Asked Questions

Common questions about the Motor Speed Calculator - Free Online Tool

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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