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Transformer turns ratio calculator

Compute a transformer's turns ratio from its primary and secondary voltage.

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Need Turns ratio (Np:Ns)? The Transformer turns ratio calculator derives it from Primary voltage (V), Secondary voltage (V) in one step. For instance, with Primary voltage (V) = 240 and Secondary voltage (V) = 12 it returns Turns ratio (Np:Ns) = 20.

How to use it

  1. Enter your values: Primary voltage (V), Secondary voltage (V).
  2. Read the result instantly: Turns ratio (Np:Ns).

Frequently asked questions

What does the Transformer turns ratio calculator actually compute?

It takes Primary voltage (V) and Secondary voltage (V) and derives Turns ratio (Np:Ns) from them. The calculation is live as you type, so the result updates on every change.

What information do I need to provide?

2 values: Primary voltage (V) and Secondary voltage (V). Nothing else is required — no account, no file upload.

Can you show a worked example?

With Primary voltage (V) = 240 and Secondary voltage (V) = 12, the calculator returns Turns ratio (Np:Ns) = 20. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

When would I actually use this?

Putting a number on a bill: what an appliance costs to run, whether a solar array covers the load, and how much heating a room actually needs.

What is the most common mistake?

Confusing power with energy. A kilowatt is a rate and a kilowatt-hour is a quantity; a 2 kW heater on for half an hour uses 1 kWh, and only the second figure appears on a bill.

What is the difference between the Transformer turns ratio calculator and the Amperage Calculator?

This one returns Turns ratio (Np:Ns); the Amperage Calculator returns Current. That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Voltage divider calculator is the closest one after this: Compute the output voltage of a two-resistor voltage divider.

Where do the figures come from, and how current are they?

The arithmetic is exact for the rating and the tariff you enter. Nameplate wattage is a maximum, not an average, and solar output depends on latitude, orientation and shading that no formula can guess.

Further reading

All guides →
How-toHow Much Does a Space Heater Cost to Run?Multiply the heater's kilowatts by hours used and your price per kWh — a 1.5 kW heater for 5 hours a day adds up fast at typical tariffs.How-toHow Many Amps Does an Appliance Draw?Divide the appliance wattage by the supply voltage to get the current in amps — the number that decides breaker size, wire, and what can share a circuit.How-toWhat Wire Gauge Do I Need?Pick wire size from the load current, run length, and allowed voltage drop — the amps decide the minimum cross-section, distance forces you thicker.ExplainerHow Many Cables Fit in a Conduit? It Is a Code Question, Not a Geometry QuestionThe 40 % limit for three or more conductors is not about whether they physically fit. It is about heat and about pulling them in without stripping the insulation — and the moment you use that space, the code takes current away from every conductor in the pipe.ExplainerThe Voltage Divider: The Formula Is Trivial, the Assumption Behind It Is NotVout = Vin·R2/(R1+R2) is only true when nothing is connected to the output. Draw current and the voltage collapses, by an amount that follows one exact law. Here is that law, the ten-times rule checked against it, and why a lower-resistance divider costs you power forever.ExplainerWhat Is Voltage Drop? Why Long Wires Lose VoltageVoltage drop is the voltage lost along a wire due to its resistance. Learn how length, gauge, and current affect it, and why it matters for your circuits.