Electrical

Electrical Power Calculator

Solve electrical input power, current or supply voltage for DC and balanced AC loads. Compare SI/US results and review the method, assumptions and related references below.

Change any input to update the calculation. Unit changes preserve the physical quantity.

CALCULATION SETUP

Inputs

Solve forPreset

Supply system

Need an input value?

Common AC Voltage System Labels ↗Single & Three-Phase Power Reference ↗

Supply voltage (line-to-line for three phase)

Need an input value?

Common AC Voltage System Labels ↗Single & Three-Phase Power Reference ↗

Current

Power factor

Need an input value?

Common AC Voltage System Labels ↗Single & Three-Phase Power Reference ↗

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YOUR CALCULATION

Results

Real input power

5.889 kW7.8972 hp

Apparent power

6.9282 kVA

Reactive magnitude

3.6497 kvar

Current

10 A

Voltage

400 V

Calculation breakdown

Result interpretation: Solve electrical input power, current or supply voltage for DC and balanced AC loads

Assumptions & checks

Electrical real input power is distinct from mechanical shaft output. AC assumes balanced sinusoidal operation; no cable sizing, motor starting or code approval.

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Input lookupSingle & Three-Phase Power Reference

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Follow the full workflow: DC wire selection by voltage drop →Follow the full workflow: Three-phase motor power and current check →

Formula

Solve electrical input power, current or supply voltage for DC and balanced AC loads

DC P=VI. Single phase P=VI·PF. Three phase P=√3·VLL·I·PF; S=P/PF; |Q|=√(S²−P²). Worked example: 400 V, 10 A, PF 0.85, three phase: P=5.889 kW, S=6.928 kVA.

Worked example

Using the default values shown in the calculator, the same formula gives the following result. This is a quick sanity check for the calculation, not a design recommendation.

Inputs

Supply system: Balanced three-phase AC
Supply voltage (line-to-line for three phase): 400 V
Current: 10 A
Power factor: 0.85

Result

Real input power: 5.889 kW
Apparent power: 6.9282 kVA
Reactive magnitude: 3.6497 kvar
Current: 10 A
Voltage: 400 V

REAL INPUTS · CLEAR METHOD

Practical worked examples

Illustrative scenarios using this page’s calculation or verified reference model. Change the assumptions for your own job.

12 V DC at 10 A

Given

Supply system: DC
Supply voltage (line-to-line for three phase): 12 V
Current: 10 A

Calculation / lookup method

DC P=VI. Single phase P=VI·PF. Three phase P=√3·VLL·I·PF; S=P/PF; |Q|=√(S²−P²). Worked example: 400 V, 10 A, PF 0.85, three phase: P=5.889 kW, S=6.928 kVA.

Result

Real input power: 0.12 kW
Apparent power: 0.12 kVA
Reactive magnitude: 0 kvar
Current: 10 A
Voltage: 12 V

For the DC model P = VI. No AC power-factor assumption is applied.

230 V single-phase at 10 A and PF 0.9

Given

Supply system: Single-phase AC
Supply voltage (line-to-line for three phase): 230 V
Current: 10 A
Power factor: 0.9

Calculation / lookup method

DC P=VI. Single phase P=VI·PF. Three phase P=√3·VLL·I·PF; S=P/PF; |Q|=√(S²−P²). Worked example: 400 V, 10 A, PF 0.85, three phase: P=5.889 kW, S=6.928 kVA.

Result

Real input power: 2.07 kW
Apparent power: 2.3 kVA
Reactive magnitude: 1.0025 kvar
Current: 10 A
Voltage: 230 V

Real power includes PF; apparent power does not. These are electrical input quantities rather than motor shaft output.

400 V three-phase at 10 A and PF 0.85

Given

Supply system: Balanced three-phase AC
Supply voltage (line-to-line for three phase): 400 V
Current: 10 A
Power factor: 0.85

Calculation / lookup method

DC P=VI. Single phase P=VI·PF. Three phase P=√3·VLL·I·PF; S=P/PF; |Q|=√(S²−P²). Worked example: 400 V, 10 A, PF 0.85, three phase: P=5.889 kW, S=6.928 kVA.

Result

Real input power: 5.889 kW
Apparent power: 6.9282 kVA
Reactive magnitude: 3.6497 kvar
Current: 10 A
Voltage: 400 V

400 V is line-to-line and the load is assumed balanced. Harmonics and phase imbalance are not modeled.

Technical references for this calculation

Reference lookupCommon AC Voltage System Labels

Frequently asked questions

What does this result tell me?

Electrical real input power is distinct from mechanical shaft output. AC assumes balanced sinusoidal operation; no cable sizing, motor starting or code approval.

How can I check the calculation?

Worked example: 400 V, 10 A, PF 0.85, three phase: P=5.889 kW, S=6.928 kVA. Review each stated input and unit; use project-specific values rather than treating the editable example as a requirement.

Reference data & method sources

DOE motor systems guide
Balanced sinusoidal AC real/apparent power and motor efficiency relationships; DC uses unity power factor.
NIST SI conversion factors
SI/US dimensional conversions. Geometry and energy balances are stated explicitly, not attributed to a design standard.