Turns Ratio

How to use this calculator

The turns ratio is the number of turns on the primary winding divided by the number on the secondary: n = Np / Ns. Enter the two turn counts and the ratio appears live, along with the equivalent voltage ratio (Vp:Vs) and current ratio (Is:Ip). A ratio greater than 1 means a step-down transformer; less than 1 means step-up.

What it means in a real circuit

The turns ratio is the single number that defines a transformer's behavior: it sets the voltage step, the current step (in the inverse ratio), and the impedance step (the square of the ratio). If a 100:50 winding gives n = 2, then a 120 V primary produces 60 V on the secondary, and the secondary can deliver twice the current of the primary (neglecting losses). Use this to verify a transformer suits your voltage conversion before wiring it up.