The transformer turns ratio calculator computes the secondary voltage, turns ratio, and current transformation for any transformer configuration. Enter primary and secondary parameters to analyze transformer behavior.
Transformer Turns Ratio Calculator
Primary Side
Secondary Side
How to Calculate Transformer Turns Ratio
A transformer transfers electrical energy between circuits through electromagnetic induction. The voltage ratio equals the turns ratio: V₁/V₂ = N₁/N₂. For an ideal transformer, power in equals power out (V₁×I₁ = V₂×I₂), so current transforms inversely to voltage.
Step-Up vs Step-Down
A step-down transformer has more primary turns than secondary turns (N₁ > N₂), reducing voltage. A step-up transformer has fewer primary turns (N₁ < N₂), increasing voltage. Power utilities use step-up transformers at generating stations (increasing voltage for efficient long-distance transmission) and step-down transformers at neighborhood substations and homes.
Frequently Asked Questions
How do I calculate the transformer turns ratio?
Turns ratio = N₁/N₂ = V₁/V₂. For a 120V to 12V transformer: ratio = 120/12 = 10:1. If the primary coil has 1000 turns, the secondary has 1000/10 = 100 turns. Power is conserved: V₁×I₁ ≈ V₂×I₂, so current transforms inversely.
How do I choose transformer VA rating?
VA (volt-amps) = secondary voltage × secondary current. For a 12V secondary delivering 5A: 12V × 5A = 60VA. Always buy a transformer rated at least 20% above your calculated VA to allow for efficiency losses and occasional peaks.
What is an isolation transformer?
An isolation transformer has a 1:1 turns ratio — same voltage in and out. It electrically isolates the output from the input, eliminating ground loop noise and providing safety isolation. Used in medical equipment, audio equipment, and test benches.
Is this transformer calculator free?
Yes, completely free with no signup required.