Transformer Sizing Calculator
Calculate transformer apparent power (kVA) and real power (kW) from voltage, current, and power factor.
How to Use the Transformer Sizing Calculator
- Enter the supply or load voltage in volts.
- Enter the maximum load current in amperes.
- Enter the power factor (default 0.8 for general industrial loads).
Use Cases
- •Sizing distribution transformers for industrial and commercial buildings.
- •Checking transformer capacity for new electrical loads.
- •Estimating energy losses in transformer installations.
Formula
Apparent Power S (kVA) = V × I / 1000. Real Power P (kW) = S × power factor.
Frequently Asked Questions
What is the difference between kVA and kW?
kVA is apparent power (total volt-amperes). kW is real power (actually doing useful work). kW = kVA × power factor. Transformers are rated in kVA because they must handle the full current regardless of power factor.
What power factor should I use?
Typical industrial loads have a power factor of 0.8–0.95. Purely resistive loads (heaters) have pf = 1.0. Motor-dominant loads typically have pf = 0.7–0.85.
Is this calculator free?
Yes, all OhMyCalc calculators are completely free to use.