Watt to Amp Calculator
Convert watts to amps instantly for DC, AC single-phase, and AC three-phase circuits. Includes NEC breaker sizing and wire gauge recommendations.
Quick Formula Cheat Sheet
The most common watt-to-amp conversions, at a glance.
- Watts to Amps at 120V (Single-Phase)
- Amps = Watts ÷ 120. Example: 1500W ÷ 120V = 12.50 amps, requiring a 20A breaker under the NEC 80% continuous load rule.
- Watts to Amps at 240V (Single-Phase)
- Amps = Watts ÷ 240. Example: 3000W ÷ 240V = 12.50 amps, requiring a 20A breaker.
- Watts to Amps at 12V (Direct Current / DC)
- Amps = Watts ÷ 12. Example: 600W ÷ 12V = 50.00 amps.
- Watts to Amps, 3-Phase (Line-to-Line)
- Amps = Watts ÷ (√3 × Power Factor × Volts). Example: 15,000W at 480V (PF 0.85) draws 21.24 amps.
Watt to Amp Formulas
The correct formula depends on your circuit type. Here is a breakdown of all three.
DC Circuits
Amps = Watts ÷ Volts
Direct current is the simplest case, covering batteries, solar panels, and automotive systems. Example: a 1200W load at 12V draws 100 amps.
AC Single-Phase
Amps = Watts ÷ (Power Factor × Volts)
Standard US household circuits at 120V or 240V. Power factor accounts for inductive loads like motors and compressors; resistive loads (heaters, lights) use PF = 1.0.
AC Three-Phase
Amps = Watts ÷ (√3 × Power Factor × Volts)
Commercial and industrial circuits at 208V or 480V. √3 (approximately 1.7320508) accounts for the phase relationship between the three conductors.
Typical Power Factor Values
Use these as starting estimates only. Always use nameplate data or a power analyzer for accurate calculations.
| Device / Load Type | Typical PF |
|---|---|
| Resistive load (heater, oven) | 1.00 |
| Incandescent lamp | 1.00 |
| Fluorescent lamp | 0.95 |
| Synchronous motor | 0.90 |
| Induction motor (full load) | 0.85 |
| Induction motor (no load) | 0.35 |
Common Watts to Amps Conversions
Quick reference table for common wattages at 12V, 120V, and 240V.*
| Watts | Amps @ 12V | Amps @ 120V | Amps @ 240V |
|---|---|---|---|
| 100W | 8.33A | 0.83A | 0.42A |
| 200W | 16.67A | 1.67A | 0.83A |
| 400W | 33.33A | 3.33A | 1.67A |
| 500W | 41.67A | 4.17A | 2.08A |
| 600W | 50.00A | 5.00A | 2.50A |
| 800W | 66.67A | 6.67A | 3.33A |
| 1000W | 83.33A | 8.33A | 4.17A |
| 1200W | 100.00A | 10.00A | 5.00A |
| 1500W | 125.00A | 12.50A | 6.25A |
| 1800W | 150.00A | 15.00A | 7.50A |
| 2000W | 166.67A | 16.67A | 8.33A |
| 2400W | 200.00A | 20.00A | 10.00A |
| 3000W | 250.00A | 25.00A | 12.50A |
* All values assume a power factor of 1.0 (purely resistive load). Inductive loads (motors, compressors) will draw more current at the same wattage, so use the calculator above with the correct power factor for accurate results.
Household Appliance Amp Draw
Typical wattage and amperage for common US household appliances.
| Appliance | Typical Watts | Voltage | Amps |
|---|---|---|---|
| LED Light Bulb | 10W | 120V | 0.08A |
| Laptop Charger | 65W | 120V | 0.54A |
| Refrigerator (running) | 400W | 120V | 3.33A |
| Gaming Console | 200W | 120V | 1.67A |
| Desktop Computer | 500W | 120V | 4.17A |
| Microwave Oven | 1000W | 120V | 8.33A |
| Coffee Maker | 1200W | 120V | 10.00A |
| Toaster | 1200W | 120V | 10.00A |
| Hair Dryer | 1800W | 120V | 15.00A |
| Space Heater | 1500W | 120V | 12.50A |
| Window Air Conditioner | 1200W | 120V | 10.00A |
| Washing Machine | 500W | 120V | 4.17A |
| Electric Dryer | 5000W | 240V | 20.83A |
| Electric Water Heater | 4500W | 240V | 18.75A |
| Electric Range/Oven | 3000W | 240V | 12.50A |
| Level 2 EV Charger | 7680W | 240V | 32.00A |
| Central Air Conditioner | 3500W | 240V | 14.58A |
| Well Pump | 1500W | 240V | 6.25A |
Popular Calculators
Jump straight to a pre-filled calculator for a specific wattage or voltage.
Frequently Asked Questions
How do I convert watts to amps?
For DC circuits, divide watts by volts (Amps = Watts ÷ Volts). For AC single-phase circuits, divide watts by the product of power factor and volts. For AC three-phase circuits, divide watts by the product of √3, power factor, and volts.
Why do I need power factor for AC calculations?
Power factor accounts for the phase difference between voltage and current caused by inductive loads like motors and compressors. Purely resistive loads (heaters, incandescent bulbs) have a power factor of 1.0. Motors typically run 0.8–0.95.
What breaker size do I need for a 1500W appliance at 120V?
1500W at 120V draws 12.50 amps. Per NEC Article 210.20, continuous loads must not exceed 80% of a breaker rated capacity, so a 15A breaker (12A max continuous) is not sufficient. A dedicated 20A circuit is required.
Does this calculator work for 240V appliances?
Yes. Enter your wattage and set voltage to 240V for dryers, water heaters, ranges, and EV chargers. At the same wattage, 240V circuits draw half the current of 120V circuits.
Is this calculator accurate for 3-phase industrial power?
Yes. Select the AC 3-Phase tab, enter your line voltage (commonly 208V or 480V), and choose line-to-line or line-to-neutral mode. The calculator uses the precise value of √3, not a rounded 1.732 approximation.
Can I use this to size wire gauge?
The calculator provides an AWG wire gauge recommendation based on NEC Table 310.15(B)(16) for 60°C copper conductors. Always confirm final wire and breaker sizing with a licensed electrician before installation.