A watts to amps calculator converts electrical power (watts) to current (amps) using the circuit voltage and, for AC circuits, the power factor. Whether you are sizing a circuit breaker, checking appliance loads, or designing a DC system, knowing the amperage is essential for safe electrical work. Use the reverse mode to convert amps back to watts.
Inputs
Default 0.85 suits most AC loads. Use 1.0 for resistive loads (heaters, incandescent bulbs).
Result
Common Appliance Reference (120 V AC, PF 1.0)
| Appliance | Watts | Amps (120 V) |
|---|---|---|
| LED bulb | 60 | 0.50 |
| Phone charger | 150 | 1.25 |
| Microwave (small) | 700 | 5.83 |
| Hair dryer | 1,200 | 10.00 |
| Space heater | 1,500 | 12.50 |
| Clothes dryer | 2,000 | 8.33 (240V) |
| Central AC unit | 5,000 | 20.83 (240V) |
| Electric water heater | 10,000 | 41.67 (240V) |
Click any row to load its values into the calculator above.
How to Use the Watts to Amps Calculator
Converting between watts and amps is one of the most common tasks in electrical work, from sizing circuit breakers to understanding appliance loads. This free watts to amps calculator handles DC, single-phase AC, and three-phase AC systems with the correct formula for each. You can also reverse it to convert amps back to watts.
Step 1: Choose a Conversion Mode
Click Watts → Amps if you know the power consumption in watts and want to find the current draw. Click Amps → Watts if you know the current and want to find the power. The input label updates automatically to reflect your selection.
Step 2: Select the Circuit Type
Choose DC for battery systems, solar panels, automotive wiring, and other direct-current circuits. Choose Single-Phase AC for standard household outlets (120 V in North America, 230–240 V in Europe and Australia). Choose Three-Phase AC for commercial and industrial systems that use multiple phase voltages such as 208 V, 277 V, or 480 V.
Step 3: Enter Watts (or Amps) and Voltage
Type the power value in the first field, then enter the circuit voltage. Use the voltage preset dropdown to quickly select common voltages: 12 V for car batteries and small DC systems, 24 V for larger DC systems, 120 V for US standard outlets, 208 V or 480 V for US commercial three-phase, and 240 V for US large appliances or UK/EU household supply.
Step 4: Set the Power Factor (AC Only)
For AC circuits, the power factor (PF) accounts for the phase difference between voltage and current. It ranges from 0 to 1. Use 1.0 for purely resistive loads like electric heaters, toasters, and incandescent light bulbs. Use 0.85 (the default) as a general estimate for most household appliances. Motors, compressors, and other inductive loads may have power factors as low as 0.7–0.8. Check the appliance nameplate for an exact value. The power factor field is hidden for DC calculations since DC circuits do not have a reactive component.
Understanding the Formulas
The tool applies the appropriate formula for each circuit type and displays it with your actual values:
- DC:
A = W / V - Single-Phase AC:
A = W / (V × PF) - Three-Phase AC:
A = W / (V × √3 × PF)
The reverse formulas for amps to watts simply multiply both sides: W = A × V for DC, and include PF (and √3 for three-phase) for AC.
Using the Reference Table
The appliance reference table at the bottom shows typical wattages and calculated amp draws for common household devices. Click any row to load its watt and voltage values directly into the calculator for further calculations or to change the circuit type.
FAQ
Is this watts to amps calculator free?
Yes, this tool is completely free to use with no limits and no signup required. All calculations run instantly in your browser and no data is sent to any server.
Is my data private when using this calculator?
Yes, everything runs locally in your browser. Your inputs are never sent to a server, stored, or tracked. You can even use the tool offline once the page has loaded.
What is the formula to convert watts to amps for DC circuits?
For DC circuits, Amps = Watts / Volts. For example, a 1200 W device running on 120 V draws 10 A. Divide the power in watts by the supply voltage to get current in amps.
How do I calculate amps for single-phase AC circuits?
For single-phase AC, Amps = Watts / (Volts × Power Factor). The power factor accounts for the phase difference between voltage and current. A typical power factor for resistive loads is 1.0, while inductive loads like motors commonly use 0.8–0.9.
How do I calculate amps for three-phase AC circuits?
For three-phase AC, Amps = Watts / (Volts × √3 × Power Factor), where √3 ≈ 1.732. Three-phase power is common in industrial and commercial settings with voltages like 208 V, 480 V, or 277 V between phases.
What is power factor and why does it matter?
Power factor (PF) is a value between 0 and 1 that describes how efficiently electrical power is converted to useful work. A PF of 1.0 means all power is used productively (resistive loads like heaters). Motors, fluorescent lights, and other inductive loads have lower power factors (0.7–0.95), meaning they draw more current than their watt rating alone implies.
What is the difference between watts and amps?
Watts (W) measure electrical power — the rate at which energy is consumed or produced. Amps (A) measure electrical current — the flow of electric charge. They are related by voltage: Power (W) = Voltage (V) × Current (A) for DC circuits. Higher voltage means fewer amps are needed to deliver the same power.
What common voltages should I use?
Common voltages include: 12 V and 24 V for automotive and DC systems; 120 V for US household outlets; 240 V for US large appliances and UK/EU household supply; 208 V and 480 V for US commercial three-phase systems; 277 V for single-phase commercial lighting. Always verify the actual voltage of your circuit before sizing wiring or breakers.