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Transformer Calculator
Estimate ideal transformer voltage, turns ratio or secondary current from the values you know. Choose one calculation mode and enter its inputs.
How do I calculate transformer voltage?
For voltage, enter primary voltage and both winding turn counts. A 100-turn primary, 50-turn secondary and 120 V input gives 60 V ideal output. Turns ratio mode uses secondary voltage divided by primary voltage; current mode uses the inverse turns ratio and your efficiency estimate.
Frequently asked questions
How do I calculate transformer voltage?
For voltage, enter primary voltage and both winding turn counts. A 100-turn primary, 50-turn secondary and 120 V input gives 60 V ideal output. Turns ratio mode uses secondary voltage divided by primary voltage; current mode uses the inverse turns ratio and your efficiency estimate.
Are my transformer values uploaded?
No. This calculator runs in your browser. It does not upload or save the values you enter.
What is the transformer turns ratio?
This calculator defines it as secondary turns divided by primary turns (Ns/Np). For an ideal transformer, the secondary-to-primary voltage ratio is the same.
How does turns ratio affect current?
In an ideal transformer, current ratio is inverse to the turns ratio. The current mode also multiplies by the efficiency percentage you enter, so it is only an estimate.
Can this choose or verify a safe transformer?
No. It does not check power rating, frequency, core saturation, temperature, insulation, fault protection or local electrical rules. Use manufacturer data and qualified engineering review.