Transformer Turns Ratio Calculator

A transformer steps voltage up or down according to the ratio of turns on its primary and secondary windings, and this calculator ties those quantities together. The turns ratio equals the primary turns divided by the secondary turns, which also equals the primary voltage divided by the secondary voltage. Enter any pair of voltages or turn counts and the tool finds the ratio, then works out the matching secondary voltage. Because power is conserved in an ideal transformer, the current transforms the opposite way, so a step down that halves the voltage doubles the available current. The calculator shows this reflected current and the ratio in a clean form. This is useful for designing power supplies, matching audio impedances, and understanding mains adapters. Enter your known values and read the full picture instantly. Everything runs locally in your browser, so it is private and immediate.