POWER · CALCULATOR

Active power calculator

Free active power calculator: get active power from voltage, current and power factor. The formula and a worked example are shown; verify against the NEC.

Written by Chameera Sampath · Not yet reviewed by a licensed electrician. See the methodology.

US (NEC) only · NFPA 70 / NEC — locally adopted editionDefaults are US values. Verify the locally adopted NEC edition and project data.Official reference ↗

Project inputs

Measurements

Voltage

Current

SupplyPower factor

Updates as inputs change. Unit changes preserve the same physical values.

THE MATH BEHIND THE ANSWER

Method & assumptions

P = k × V × I × PF

Balanced AC or DC; not mechanical motor output.

Results do not check every aspect of an electrical installation. The calculators follow US (NEC) practice only; a regional preset changes defaults such as voltage and units, and no result certifies NEC compliance.

Sources and validation →

Worked example

Voltage: 120 V · Current: 20 A · Supply: Single phase · Power factor: 0.85

Active power: 2.04 kW

This example uses the stated inputs; results for the entered values appear above.

Explore the power branch →See the related electrical concepts →

Estimating and invoicing tool

Ampxa is developing an estimating and invoicing application for electrical contractors. The list below receives notice when it opens.