Transformer Turns Ratio Calculator
Voltage, current and turns for a transformer.
Enter your values
Results update instantly as you type — no submit needed.
Results
- Turns ratio
- 20:1
- Secondary turns
- 40
- Primary current
- 0.15 A
- Power
- 36 VA
Quick answer
Transformer voltage ratio equals the turns ratio, while current ratio is its inverse.
Vp ÷ Vs = Np ÷ Ns
How to use the Transformer Turns Ratio Calculator
- 1Enter primary and secondary voltages.
- 2Enter the primary turns count.
- 3Enter secondary current for the power figure.
Frequently asked questions
Are real transformers lossless?
No — expect 90–97% efficiency, so primary current is slightly higher.
Can it step up?
Yes — set secondary voltage above primary for a step-up ratio.