Transformer Turns Ratio Calculator

An ideal transformer couples two windings through a shared magnetic core, and the voltage across each winding is proportional to how many turns it has: Vp/Vs = Np/Ns. Because an ideal (lossless) transformer passes the same power through both sides (Vp×Ip = Vs×Is), the current ratio runs the exact opposite way — a step-down in voltage is always matched by an equal step-up in current, and vice versa: Is/Ip = Np/Ns.

Given the primary winding's turns, voltage, and current plus the secondary's turns, this calculator solves directly for the secondary's voltage (Vs = Vp × Ns/Np) and current (Is = Ip × Np/Ns). Primary and secondary power are reported separately rather than assumed identical, so the result makes the ideal, no-loss assumption visible — a real transformer's secondary power is always slightly less than its primary due to core and winding losses this calculator doesn't model.