POWER · CALCULATOR

Primary and secondary transformer winding

Free primary and secondary transformer winding: get secondary turns and turns ratio from primary turns, primary voltage and secondary voltage.

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

Primary turns

Primary voltage

Secondary voltage

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

THE MATH BEHIND THE ANSWER

Method & assumptions

Ns / Np = Vs / Vp

Ideal transformer ratio; not winding conductor, core or insulation design.

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

Primary turns: 1,000 · Primary voltage: 120 V · Secondary voltage: 24 V

Secondary turns: 200 turns · Turns ratio: 5

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

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