Transformer Turns Ratio Calculator

Solve the ideal-transformer ratios between primary and secondary voltage, current, turns and impedance. In a perfect transformer the turns ratio a = Np/Ns equals Vp/Vs and Is/Ip, and the impedance seen at the primary is a² times the load: Vp·Ip = Vs·Is and Zp = a²·Zs. Enter the primary and secondary voltage to get the turns ratio and the current ratio, and optionally the load current or load impedance to get the primary current, reflected impedance and apparent power. Or switch to impedance-matching mode and enter a source and load impedance to find the turns ratio that matches them. Useful for power-supply and mains transformer design, audio output and interstage transformers, and RF/antenna matching. Pure arithmetic — ideal lossless equations; real transformers add winding resistance, leakage inductance, core loss, magnetising current, frequency-dependent coupling and regulation, so size the core and wire for the real losses. Everything runs locally in your browser.