Transformer Power Calculator

Calculate transformer power ratings for any load. Switch single or three phase, adjust factors easily. Get kVA, kW, input power, and losses instantly today.

Inputs

Three-phase assumes line-to-line voltage.
Load mode scales current by load percent.
Use 100 for full-load, 75 for partial.
For three-phase, enter line-to-line voltage.
Enter line current for three-phase systems.
Used to estimate real power from kVA.
Typical: 90–99% depending on size.
Reset

Formula Used

Single-phase apparent power
S = V × I
S in VA, V in volts, I in amps.
Three-phase apparent power
S = √3 × VL-L × IL
Assumes line-to-line voltage and line current.
Real power and losses
Pout = S × PF × η
η is efficiency as a decimal. Input power Pin = Pout / η. Losses = Pin − Pout.

Notes: This calculator estimates electrical power from measured voltage and current. Actual ratings also depend on temperature rise, cooling, harmonics, and nameplate limits.

How to Use This Calculator

  1. Select single-phase or three-phase based on your system.
  2. Enter voltage and current with the correct units.
  3. Choose rated mode, or load mode to scale current.
  4. Set power factor and efficiency for real power estimates.
  5. Press Calculate to view results above the form.
  6. Use the CSV button to export values for records.
  7. Use the PDF button to print or save results.

Example Data Table

Phase Voltage Current PF Efficiency Apparent (kVA) Output (kW) Losses (kW)
Single 230 V 10 A 0.90 95% 2.3000 1.9665 0.1035
Three 400 V 15 A 0.85 96% 10.3923 8.4775 0.3532
Three 11 kV 0.25 A 0.95 98% 4.7631 4.4342 0.0905

Example outputs are rounded and shown for learning purposes.

Related Calculators

rc time constant calculatorresistivity calculatorelectric flux calculatorinductive reactance calculatorrms voltage calculatorrms current calculatorled series resistor calculatormagnetic flux calculatorrl time constant calculatorcurrent density calculator

Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.