Transformer Turns Ratio Calculator
An ideal transformer’s voltage ratio follows its primary-to-secondary winding-turn ratio. Use this tool for a first-pass turns ratio and secondary-voltage estimate.
How to use this calculator
- Enter positive primary and secondary turn counts plus the primary voltage. The result assumes an ideal transformer.
- Check the labels and units before applying the result to a real task.
- Change one input at a time when comparing scenarios.
Formula and method
Vs/Vp = Ns/Np, so Vs = Vp × Ns/Np
- Vs/Vp = Ns/Np, so Vs = Vp × Ns/Np
- Real transformers have losses and voltage regulation effects. This arithmetic does not verify insulation, current limits, protection or electrical safety.
Worked examples
Worked example
A transformer has 1,000 primary turns, 200 secondary turns and a 230 V primary input.
The turns ratio Ns/Np is 0.2, so ideal secondary voltage is 230×0.2 = 46 V.
The turns ratio Ns/Np is 0.2, so ideal secondary voltage is 230×0.2 = 46 V.
Understanding the result
An ideal transformer’s voltage ratio follows its primary-to-secondary winding-turn ratio. Use this tool for a first-pass turns ratio and secondary-voltage estimate.
Real transformers have losses and voltage regulation effects. This arithmetic does not verify insulation, current limits, protection or electrical safety.
Important notes
Real transformers have losses and voltage regulation effects. This arithmetic does not verify insulation, current limits, protection or electrical safety.
Displayed values are rounded for readability; retain appropriate precision when continuing a calculation.
Frequently asked questions
What is a step-down transformer?
An ideal transformer with fewer secondary than primary turns gives a lower secondary voltage. A higher secondary turns count gives a step-up relationship.
Does the turns ratio specify output current?
Current relationships depend on loading and power balance. This calculator focuses on turns ratio and ideal voltage only.
Can I use the result to build a mains transformer?
No. Design and construction require electrical engineering, insulation, core, thermal, winding and regulatory considerations beyond this estimate.
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Related explanations
Learn the method behind the number or compare the terminology before using the calculator.
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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.