Your doorbell runs on 16 volts but your house delivers 120 — a small transformer on the wall makes the peace. A transformer trades voltage for current through its turns ratio: the secondary voltage equals the primary voltage times the secondary turns divided by the primary turns, V_s = V_p × (N_s/N_p). More turns on the secondary steps the voltage up; fewer steps it down, which is why the little beige box by your electrical panel hums quietly at 16 volts while the grid roars at thousands upstream.

This calculator applies the turns ratio. Type the primary voltage in volts into Variable A — 120 for a US wall circuit — and the turns ratio N_s/N_p as a decimal into Variable B; the Result box gives the secondary voltage. A homeowner in Ohio replacing a doorbell transformer, for instance, enters 120 in Variable A and 0.133 in Variable B and reads 16 volts, the standard chime voltage. Power is conserved (minus small losses), so halving the voltage doubles the available current — the reason the thin doorbell wire survives while the 120-volt feed needs proper gauge. Model railroads, HVAC control circuits, and phone chargers all hide a transformer doing exactly this.

With the pre-filled defaults — Variable A 10, Variable B 5 — the Transformer Calculator returns Result 50.0000. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.