🔄 Transformer Ratio Calculator for Electrical
Estimate ideal secondary voltage and current from a turns ratio.
This free tool helps you turn project measurements into a practical planning estimate. Enter values in Vaelden’s interactive calculator, review the result, and confirm important assumptions against supplier data, measurements, codes or qualified advice before committing materials or money.
Open the Transformer Ratio calculator →
How to calculate transformer ratio
Method: Secondary voltage = primary voltage × secondary turns ÷ primary turns
- Use the primary RMS voltage and turns.
- Apply the turns ratio for ideal secondary voltage.
- Check load VA and expected regulation separately.
Worked example
Using these planning inputs:
- Primary voltage: 230 V
- Primary turns: 1000
- Secondary turns: 100
- Secondary load: 100 VA
Ideal secondary voltage: 23.00 V
Reality check: This ideal model excludes core flux, losses, insulation, temperature rise, inrush and fault protection; transformer construction requires specialist design.
Before you calculate
Use consistent units and the best measured inputs available. Real materials, equipment, site conditions and tolerances can change the result. Vaelden shows planning estimates; regulated, structural, electrical, plumbing, pressure and other safety-critical work still requires appropriate local compliance and professional advice.