MAXScanner engineering calculator
Updated 2026-09-18
Transformer Turns Ratio Calculator — Voltage, Current & Apparent Power
Solve an ideal transformer from primary and secondary turns, primary voltage and current. Get turns ratio, secondary voltage/current, apparent power and step-up or step-down classification.
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Your calculation, step by step
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- 1.Turns ratio Np:Ns: Np ÷ Ns = 1,000 ÷ 100 = 10:1.
- 2.Secondary voltage: Vp ÷ ratio = 230 ÷ 10 = 23 V.
- 3.Secondary current: Ip × ratio = 1 × 10 = 10 A.
- 4.Ideal apparent power: Vp × Ip = 230 × 1 = 230 VA.
Formula, example and limits
Np/Ns = Vp/Vs = Is/Ip; S ≈ VpIp ≈ VsIs for an ideal transformer.
1000 primary turns, 100 secondary turns and 230 V primary gives about 23 V secondary.
- Ideal transformer with negligible winding loss and magnetizing current.
- Real regulation, copper loss, core loss, saturation and temperature require datasheet or measured values.
Frequently asked questions
Does a step-down transformer increase current?
In the ideal model, yes. Lower secondary voltage corresponds to proportionally higher secondary current at the same apparent power.
Can I use this as a final transformer design?
No. It is ratio and loading math; real transformer design also needs core area, flux density, frequency, wire gauge, thermal rise and regulation checks.
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