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Science & Engineering

Electrical Power Calculator

Calculate real, apparent and reactive power for DC, single-phase AC and three-phase AC circuits from voltage, current and power factor.

Your inputs

Results

Real power

2.07 kW

Apparent power
2.3 kVA
Reactive power
1.0025 kVAR
Real power
2,070 W

✓Exact calculation — rounded only for display

Notes for this result

  • Educational estimate. Electrical, structural and other safety-critical work must follow local codes and be checked by a qualified professional.

What this calculator does

In AC circuits, real power (kW) depends on the power factor; apparent power (kVA) sizes cables and generators.

Formula and method

S = V × I (single-phase) or √3 × V_LL × I (three-phase); P = S × PF; Q = S × √(1 − PF²)

Worked example

Calculated by this tool with its default inputs:

Inputs

  • System: AC single-phase
  • Voltage: 230 V
  • Current: 10 A
  • Power factor: 0.9

Results

  • Real power: 2.07 kW
  • Apparent power: 2.3 kVA
  • Reactive power: 1.0025 kVAR
  • Real power: 2,070 W

How to read the results

A low power factor means more current for the same useful power.

Assumptions and limitations

  • Assumes balanced three-phase loads and sinusoidal waveforms.
  • Educational estimate. Electrical, structural and safety-critical work must follow local codes and be designed or checked by a qualified professional.

These are educational estimates. Electrical, structural and other safety-critical work must comply with local codes and be designed or checked by a qualified professional.

Questions

kW or kVA?

kW is useful power; kVA is total power including the reactive part.

Methodology and verification

Result type
Exact mathematical calculation (rounded only for display)
Formula version
1.0
Automated verification
4 reference and validation test cases, checked against independently computed values. The site cannot be built if any of them fail.
Editorial review
Awaiting human editorial review. The explanation was drafted with AI assistance; the formula and examples are verified by the automated tests above.

Privacy

Everything you enter is calculated in this browser and is not sent to Numerith or anyone else. Inputs are added to a share link only if you choose to include them. Privacy policy