Transformer turns ratio calculator

V_p / V_s = N_p / N_s = I_s / I_p. Ideal transformer: same VA on both sides. Step-up: V_s > V_p (turns ratio < 1). Step-down: V_s < V_p (turns ratio > 1).

Primary (input)

Primary voltage V_p (V)

Primary turns N_p

Secondary (output)

Secondary voltage V_s (V)

Secondary turns N_s

Primary current I_p (A)

Secondary current I_s (A)

Fill any 2–3 known values; leave the rest at 0.

Turns ratio (N_p:N_s)

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Type

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Computed V_s

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Computed N_s

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Computed I_p

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Power (VA)

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Conservation of power

An ideal transformer transfers all power: V_p × I_p = V_s × I_s. So stepping voltage up 10× steps current down 10× — the wire on the high-voltage side carries less current and can be thinner.

Real transformers: 95–99% efficient. Loss = core (magnetisation) + copper (I²R).
Turn count is approximate — for real winding, calculate volts per turn from core area + frequency.