Watts / amps / volts calculator

DC: P = V × I. Single-phase AC: P = V × I × cosφ. Three-phase AC: P = √3 × V_line × I × cosφ. Choose the system and supply any two values.

System

Solve for

First input

Second input

Power factor (cos φ) — AC only

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DC: inputs are V and I. Output: P.

Voltage

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Current

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Power

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Power factor

For resistive loads (incandescent bulbs, heaters) cosφ ≈ 1. For motors, fluorescent ballasts and switching power supplies it’s typically 0.7–0.9. Industry equipment often must be above 0.95 to avoid utility penalties.