Transformer Turns Ratio Calculator
Find the secondary side of an ideal transformer from the primary values.
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Transformer Turns Ratio Calculator by TheCalcTools
How the Transformer Turns Ratio Calculator works
Enter the primary and secondary voltages, the number of primary turns and the primary current.
In an ideal transformer, voltage scales with turns.
Power in equals power out, so current scales inversely.
The formula
Worked example
Using the default values shown in the calculator:
| Primary voltage (V) | 230 |
|---|---|
| Secondary voltage (V) | 12 |
| Primary turns | 1000 |
| Primary current (A) | 0.5 |
- Turns ratio = 230 ÷ 12 = 19.17.
- Secondary turns = 1,000 × 12 ÷ 230 = 52.2.
- Secondary current = 0.5 × 230 ÷ 12 = 9.583 A.
Result:
| Turns ratio (Np ÷ Ns) | 19.1667 |
|---|---|
| Secondary turns | 52.2 |
| Secondary current (A) | 9.583 |
| Power (VA) | 115.00 |
Frequently asked questions
Is a real transformer ideal?
No. Real ones lose a few percent to winding resistance and core losses, so secondary current will be a little lower.
Can a transformer work on DC?
No. It needs a changing magnetic flux, so it works only on AC or pulsed signals.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.