Amps to Watts Calculator
Convert electrical current in amps to power in watts and kilowatts for DC, single-phase AC, and three-phase AC circuits.
Calculator Inputs
Power Result
How to use this calculator
- Pick your circuit configuration. Select whether the power supply is DC, single-phase AC, or balanced three-phase AC.
- Input current and voltage. Enter the measured or rated current in amps (A) and the supply voltage in volts (V).
- Specify the power factor for AC. For alternating current, provide the power factor (typically 1.0 for resistive loads, 0.8 to 0.9 for motors).
- Review the results. The calculator outputs both real power in watts (W) and kilowatts (kW) instantly.
Formulas
Power calculations based on current and voltage:
- Direct Current (DC): P = V × I
- AC Single Phase: P = V × I × PF
- AC Three Phase (Line-to-Line): P = √3 × V × I × PF
Where P is power in watts, V is voltage in volts, I is current in amps, and PF is power factor.
Worked Example
Calculate power for an appliance drawing 10 A on a 230 V single-phase AC circuit with PF = 1.0:
- Formula: P = V × I × PF
- Calculation: P = 230 × 10 × 1.0 = 2300 W (2.3 kW)
The circuit delivers 2300 watts of real electrical power.
Frequently Asked Questions
Why can I not convert amps to watts directly without voltage?
Amps measure electrical current flow, whereas watts measure the rate of energy consumption. Without voltage driving the current, total power cannot be determined.
How do I calculate watts for a single-phase AC circuit?
Multiply current by voltage and the load's power factor: P = V × I × PF. For a purely resistive load where PF is 1.0, power is simply volts multiplied by amps.
What is the difference between watts (W) and kilowatts (kW)?
One kilowatt equals 1,000 watts. To convert watts to kilowatts, divide by 1,000. For instance, 2,300 W equals 2.3 kW.
Where does the square root of 3 come from in three-phase power?
In a balanced three-phase system, the phase conductors are 120 degrees apart. The factor √3 (approximately 1.732) accounts for the geometric relationship between line-to-line and phase voltages.
Does direct current have a power factor?
No. In DC systems, current and voltage do not oscillate, so there is no phase angle. The power factor is effectively 1.0, and power is always P = V × I.
How does circuit power relate to generator or transformer sizing?
Generators and transformers are usually rated in apparent power (kVA). Divide real power in kW by the power factor to find the required kVA.
Disclaimer
This calculator is provided for educational and estimation purposes only. Always consult a licensed electrical professional and adhere to your local electrical codes and standards before making any decisions based on these calculations.
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