Watts to Amps Calculator
This watts to amps calculator converts between watts and amps for DC and AC circuits. Includes power factor input and an appliance reference table.
About Watts to Amps Calculator
This calculator converts between watts and amps for direct current (DC), single-phase AC, and three-phase AC circuits. It is a practical tool for electricians, engineers, homeowners, and anyone working with electrical systems.
Bidirectional Conversion
Switch between watts to amps and amps to watts depending on what you need to find. Enter the values you know and the calculator solves for the unknown. The formula used is displayed alongside the result so you can verify the math.
DC and AC Support
Select from DC, single-phase AC, or three-phase AC circuit types. Each type uses the appropriate formula. AC calculations include a power factor input, which accounts for the phase difference between voltage and current that reduces effective power delivery. DC calculations use the simpler watts = volts x amps relationship.
Common Appliance Reference
A built-in reference table lists typical wattage values for common household and commercial appliances. This helps you quickly look up values when you do not have a device's specifications handy. Examples include light bulbs, microwaves, air conditioners, and power tools.
Practical Applications
Use this tool to determine if a device will overload a circuit, to select the correct wire gauge for an installation, or to size a generator for your power needs. Understanding the relationship between watts, amps, and volts is essential for safe electrical work and energy planning. To estimate how much your appliances cost to run, try the electricity cost calculator.
All calculations are performed in your browser. No data is sent to any server.
Frequently Asked Questions
What is the formula for converting watts to amps?
For DC circuits, amps = watts / volts. For single-phase AC, amps = watts / (volts x power factor). For three-phase AC, amps = watts / (volts x power factor x square root of 3). The power factor accounts for the phase difference between voltage and current in AC circuits.
What is power factor and what value should I use?
Power factor is a number between 0 and 1 that represents how efficiently electrical power is being used in an AC circuit. A power factor of 1.0 means all power is being used effectively. Typical residential loads have a power factor around 0.8 to 0.95. If you are unsure, 0.85 is a reasonable default for mixed household loads.
What is the difference between DC and AC power calculations?
DC (direct current) flows in one direction and the calculation is straightforward - watts equals volts times amps. AC (alternating current) changes direction periodically, which introduces power factor into the equation. Single-phase AC is typical in homes, while three-phase AC is used in industrial and commercial settings.
Why do I need to know amps for my electrical circuits?
Knowing the amperage draw of devices helps you select the correct wire gauge, choose appropriately rated circuit breakers, and avoid overloading circuits. For example, a standard US household circuit is rated for 15 or 20 amps, so knowing your device draws 12 amps tells you it can safely run on that circuit.
Can I use this calculator for three-phase power systems?
Yes. Select the three-phase AC option, enter the line-to-line voltage, wattage, and power factor. The calculator applies the three-phase formula which includes the square root of 3 (approximately 1.732) multiplier. This is commonly used for industrial motors, large HVAC systems, and commercial equipment.