Watts to Amps Calculator
Convert electrical power in watts to current in amps for DC, single-phase AC, and three-phase AC circuits. Features unit dropdowns (mW–MW, mA–kA), adjustable power factor, wire gauge recommendations, and appliance reference tables.
How to Convert Watts to Amps
Converting watts to amps tells you how much current flows through your circuit—critical information for selecting wire gauge, circuit breakers, and ensuring safety. This is the most comprehensive watts to amps calculator online, with features no competitor offers: unit dropdowns, power factor presets, and automatic wire gauge recommendations.
Select Circuit Type
Choose DC, single-phase AC, or three-phase AC. Each uses a different formula for accurate results.
Enter Values with Units
Input power (mW–MW) and voltage (mV–kV). For AC, set power factor using presets or a custom value.
Get Current + Wire Size
Current is shown in amps (and milliamps for small values) with a recommended wire gauge based on NEC.
Watts to Amps Formula
Example Calculations
A car amplifier drawing 500W from a 12V battery needs heavy gauge wire and a proper fuse.
Solar array to charge controller. Higher voltage (48V) would halve the current to 20.83A.
A 2kW appliance on 240V. The power factor of 0.9 adds ~11% more current than PF=1.
An industrial motor. Three-phase at 480V keeps current very low for 5kW of power.
Draws 83% of a 15A circuit. NEC 80% rule says max 12A continuous—this needs a 20A circuit for continuous use.
Watts to Amps Conversion Table (DC / PF=1)
| Watts | 12V | 24V | 120V | 208V | 240V | 480V |
|---|---|---|---|---|---|---|
| 100W | 8.33A | 4.17A | 0.83A | 0.48A | 0.42A | 0.21A |
| 500W | 41.67A | 20.83A | 4.17A | 2.40A | 2.08A | 1.04A |
| 1,000W | 83.33A | 41.67A | 8.33A | 4.81A | 4.17A | 2.08A |
| 1,500W | 125A | 62.50A | 12.50A | 7.21A | 6.25A | 3.13A |
| 2,000W | 166.67A | 83.33A | 16.67A | 9.62A | 8.33A | 4.17A |
| 3,000W | 250A | 125A | 25A | 14.42A | 12.50A | 6.25A |
| 5,000W | 416.67A | 208.33A | 41.67A | 24.04A | 20.83A | 10.42A |
Wire Gauge Selection by Amperage (NEC)
Selecting the correct wire gauge for the calculated amperage is critical for safety. Using undersized wire can cause overheating, insulation failure, and electrical fires. This table follows NEC Article 310 for copper conductors at 60°C (most common residential rating).
| Wire Gauge (AWG) | Max Amps (60°C) | Max Amps (75°C) | Common Use | Breaker Size |
|---|---|---|---|---|
| 14 AWG | 15A | 20A | Lighting, general outlets | 15A |
| 12 AWG | 20A | 25A | Kitchen, bathroom, garage outlets | 20A |
| 10 AWG | 30A | 35A | Dryers, water heaters, AC units | 30A |
| 8 AWG | 40A | 50A | Electric ranges, EV chargers | 40A |
| 6 AWG | 55A | 65A | Sub-panels, large equipment | 50–60A |
| 4 AWG | 70A | 85A | Service entrance, heavy motors | 70A |
| 2 AWG | 95A | 115A | Main service panels | 100A |
| 1/0 AWG | 125A | 150A | Main service entrance | 125–150A |
Common Appliance Current Draw Reference
| Appliance | Watts | Voltage | Amps | Wire / Breaker |
|---|---|---|---|---|
| LED Bulb | 12W | 120V | 0.1A | 14 AWG / 15A shared |
| Laptop | 65W | 120V | 0.54A | 14 AWG / 15A shared |
| Refrigerator | 150W | 120V | 1.25A | 12 AWG / 20A |
| Microwave | 1,200W | 120V | 10A | 12 AWG / 20A dedicated |
| Space Heater | 1,500W | 120V | 12.5A | 12 AWG / 20A dedicated |
| Window AC | 1,500W | 120V | 12.5A | 12 AWG / 20A |
| Clothes Dryer | 5,400W | 240V | 22.5A | 10 AWG / 30A |
| Electric Range | 9,600W | 240V | 40A | 8 AWG / 50A |
| EV Charger (L2) | 9,600W | 240V | 40A | 8 AWG / 50A |
| Central AC (3-ton) | 3,500W | 240V | 14.6A | 10 AWG / 30A |
⚠️ Safety: Wire Sizing & Circuit Protection
- NEC 80% Rule (Article 210.20): Continuous loads (running 3+ hours) must not exceed 80% of the breaker rating. A 15A circuit = 12A max continuous = 1,440W at 120V. A 20A circuit = 16A = 1,920W.
- Voltage drop: For long cable runs (>50ft), voltage drop increases. Use one gauge thicker than the amperage table suggests, or calculate V_drop = I × R_wire. NEC recommends max 3% voltage drop for branch circuits.
- Never exceed ratings: Using 14 AWG wire on a 20A circuit is a code violation and fire hazard. The wire overheats before the breaker trips.
- Three-phase wiring: All three-phase circuits require professional installation. Incorrect phase connections can cause motor damage, equipment failure, or back-feeding that endangers utility workers.
Understanding Watts to Amps Conversion
Converting watts to amps is the most common electrical calculation for residential and commercial work. Whether you're determining what size circuit breaker to install, selecting the appropriate wire gauge, or checking if your electrical panel can handle a new appliance, knowing the current draw is essential.
For DC circuits, the conversion is straightforward: divide power by voltage. However, AC circuits introduce the concept of power factor, which accounts for the phase difference between voltage and current waveforms. Reactive loads like motors and transformers have power factors less than 1.0, meaning they draw more current than the simple P/V formula suggests. A 1,000W motor with PF=0.8 actually draws 10.42A at 120V, not 8.33A—a 25% difference that matters for wire and breaker sizing.
Three-phase power, used in industrial settings, delivers more power using less current per conductor. The √3 factor in the three-phase formula accounts for the 120° phase offset between the three voltage waveforms, which distributes the load evenly across all three conductors.
Need the reverse conversion? Use our Amps to Watts Calculator. For AC circuits specifically, our AC Wattage Calculator also outputs apparent power (VA) and reactive power (VAR) alongside real power — useful when you need the full power triangle. For voltage conversions, try our Watts to Volts Calculator. For transformer sizing, visit our Transformer Calculator.