MOTORS · CALCULATOR

Motor synchronous speed calculator

Free motor synchronous speed calculator: get synchronous speed from frequency and number of poles. The formula is shown; verify against the NEC.

Written by Chameera Sampath · Not yet reviewed by a licensed electrician. See the methodology.

US (NEC) only · NFPA 70 / NEC — locally adopted editionDefaults are US values. Verify the locally adopted NEC edition and project data.Official reference ↗

Project inputs

Measurements

Frequency

Number of poles

Updates as inputs change. Unit changes preserve the same physical values.

THE MATH BEHIND THE ANSWER

Method & assumptions

Ns = 120f / poles

Physical motor poles must be even. Induction rotor speed is lower in motor operation.

Results do not check every aspect of an electrical installation. The calculators follow US (NEC) practice only; a regional preset changes defaults such as voltage and units, and no result certifies NEC compliance.

Sources and validation →

Worked example

Frequency: 60 Hz · Number of poles: 4

Synchronous speed: 1,800 rpm

This example uses the stated inputs; results for the entered values appear above.

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