Transformer Turns Ratio Calculator
Calculate transformer turns ratio, output voltage, and current.
Convert between primary and secondary winding specifications.
Transformer turns ratio determines how voltage is stepped up or stepped down between the primary and secondary windings.
Turns ratio formula:
Turns Ratio (a) = N₁ / N₂ = V₁ / V₂
Where:
- N₁ = number of turns on the primary winding
- N₂ = number of turns on the secondary winding
- V₁ = primary voltage
- V₂ = secondary voltage
Voltage relationship:
V₂ = V₁ × (N₂ / N₁)
Current relationship (ideal transformer):
I₂ = I₁ × (N₁ / N₂)
When voltage goes up, current goes down proportionally (conservation of power).
Power relationship:
P₁ = P₂ (ideal) or P₂ = P₁ × Efficiency
Typical transformer efficiency: 95–99% for power transformers.
Common transformer types:
| Type | Typical Ratio | Application |
|---|---|---|
| Step-down (power supply) | 10:1 to 20:1 | 120V/240V to 5V–24V |
| Step-up (power grid) | 1:10 to 1:100 | Generator to transmission line |
| Isolation (1:1) | 1:1 | Safety isolation, noise filtering |
| Audio output | 10:1 to 50:1 | Tube amplifiers to speakers |
| Current transformer | 100:1 to 1000:1 | Power measurement |
Wire gauge and turns: The number of turns determines voltage, while wire gauge determines current capacity. More turns of thinner wire = higher voltage, less current. Fewer turns of thicker wire = lower voltage, more current.
Example calculation: A transformer with 500 primary turns and 50 secondary turns:
- Turns ratio = 500/50 = 10:1 (step-down)
- If primary voltage is 120V: secondary = 120/10 = 12V
- If primary current is 1A: secondary = 1 × 10 = 10A
Tip: Real transformers have losses (copper losses in wire, core losses in iron). Account for 2–5% loss in typical power transformers. For audio transformers, frequency response and impedance matching are also important factors.