Transformer Turns Ratio Calculator
Calculate the turns ratio of an ideal transformer.
Find secondary voltage, secondary turns, or current ratio from the transformer equations.
An ideal transformer transforms voltages and currents using Faraday’s law of electromagnetic induction:
V₁/V₂ = N₁/N₂ = I₂/I₁
Where:
- V₁ = Primary voltage, V₂ = Secondary voltage
- N₁ = Primary turns, N₂ = Secondary turns
- I₁ = Primary current, I₂ = Secondary current
Key principles:
- Voltage ratio equals turns ratio: More turns on the secondary = higher voltage
- Current ratio is inverse: More turns on the secondary = less current
- Power is conserved (ideal): P₁ = P₂, so V₁I₁ = V₂I₂
- A step-up transformer increases voltage and decreases current
- A step-down transformer decreases voltage and increases current
Why power lines use high voltage:
Power transmission uses step-up transformers (e.g., 11 kV → 400 kV) before long-distance transmission lines. Why? At higher voltage, less current is needed for the same power. Less current means less resistive loss (P_loss = I²R). Long-distance lines at high voltage lose far less energy than at low voltage. Step-down transformers then reduce the voltage before reaching homes.
Real transformer efficiency: Real transformers have core losses (hysteresis, eddy currents) and copper losses (I²R in windings). Typical efficiency: 95–99% for large power transformers, 80–95% for small signal transformers.