Transformer Turns Ratio Calculator
Calculate transformer turns ratio and secondary turns.
Interactive Electrical Calculator
Transformer Turns Ratio Calculator
Calculate transformer turns ratio and secondary turns.
Result
Enter values and calculate.
About the Transformer Turns Ratio Calculator
The Transformer Turns Ratio Calculator is a free, browser-based tool for transformer sizing and turns-ratio calculations. Calculate transformer turns ratio and secondary turns. Transformer sizing calculations feed directly into upstream breaker and conductor sizing, so an error here tends to cascade into the rest of a design.
It's aimed at electricians and engineers selecting or troubleshooting step-up and step-down transformers, who need a fast, reliable number without redoing the math by hand each time.
How the calculation works
Behind the scenes, the calculation follows:
Np/Ns = Vp/Vs; Ns = Np × Vs/Vp.
Where each input maps to a field in the calculator above:
- Primary Voltage in V.
- Secondary Voltage in V.
- Primary Turns in turns.
You can adjust any of these values as many times as you like; the result updates on every change with nothing sent off your device.
A worked example
For example, start with 230 V for primary voltage, 12 V for secondary voltage and 1000 turns for primary turns. Press Calculate and the Transformer Turns Ratio Calculator returns the result instantly — then change one field at a time to see how sensitive the answer is to that particular input.
When to use the Transformer Turns Ratio Calculator
Typical reasons people reach for the Transformer Turns Ratio Calculator:
- Sizing a transformer for a known kVA or kW load.
- Working out the turns ratio needed to step a voltage up or down to a target value.
- Checking a transformer nameplate ratio against a measured voltage.
- Planning a transformer replacement or upgrade for growing load.
Good practice: Inrush current when a transformer first energizes can be many times its rated current for a brief period, which matters for upstream protective-device selection.
Also worth knowing: Transformer kVA rating should be checked against total connected load with an appropriate safety margin, not the bare minimum needed today.
Frequently asked questions
What does the Transformer Turns Ratio Calculator calculate?
Calculate transformer turns ratio and secondary turns.
How accurate is this calculator?
The formula above is applied exactly to the values you enter, so the math itself is precise. Real-world results can still differ due to component tolerances, temperature, installation method, equipment efficiency and local code requirements, so treat the output as a strong planning estimate and verify final designs against manufacturer data and the electrical code that applies to your installation.
Is this calculator free to use?
Yes. The Transformer Turns Ratio Calculator is completely free, with no account, download or installation required.
What happens if I get this wrong?
Turns ratio is what actually sets a transformer's voltage transformation, and getting it wrong is a common cause of an installation that delivers the wrong output voltage.
Will this work for both metric and everyday values?
The Transformer Turns Ratio Calculator works on any modern browser, phone or desktop, and recalculates as soon as you press Calculate. If a result looks off, double-check that every field is filled in with the unit shown next to it (mixing up units, such as W with kW, is the most common cause of an unexpected answer) and re-enter the values.