Watts to Amps Calculator
Converting watts to amps is one of the most fundamental calculations in electrical work. Whether you are sizing a circuit breaker, selecting the right wire gauge, or verifying that a load will not trip a breaker, knowing the amperage draw of a device from its wattage rating is essential. This calculator makes the conversion instant—enter the wattage and voltage, and the amperage appears automatically.
The relationship between watts, amps, and volts is defined by the power formula. Watts measure the rate of energy consumption, volts measure electrical pressure, and amps measure the flow of current. In residential work, most circuits operate at 120V or 240V, while commercial and industrial systems may run at 208V, 277V, or 480V.
Electricians use this conversion daily when planning branch circuits, calculating load totals for panels, and ensuring wire and breaker sizes comply with NEC requirements. A load rated at 1,800 watts on a 120V circuit draws 15 amps—the full capacity of a 15A breaker—which means it needs a dedicated 20A circuit to meet the 80% continuous load rule.
Watts to Amps Formula
Amps = Watts ÷ Volts
For DC and single-phase AC circuits
Common Wattage to Amperage Conversions
| Watts | 120V Amps | 240V Amps |
|---|---|---|
| 100 W | 0.83 A | 0.42 A |
| 500 W | 4.17 A | 2.08 A |
| 1,000 W | 8.33 A | 4.17 A |
| 1,500 W | 12.5 A | 6.25 A |
| 2,000 W | 16.67 A | 8.33 A |
| 3,000 W | 25.0 A | 12.5 A |
| 5,000 W | 41.67 A | 20.83 A |
How to Use This Calculator
- Enter the wattage — the power rating of the device or total load in watts.
- Enter the voltage — defaults to 120V for standard US residential circuits. Change to 240V for dryers, ranges, or other 240V loads.
- Read the result — the amperage draw is calculated instantly.
Frequently Asked Questions
How do you convert watts to amps?
To convert watts to amps, divide the wattage by the voltage. The formula is: Amps = Watts / Volts. For example, a 1,500-watt heater on a 120-volt circuit draws 12.5 amps (1500 / 120 = 12.5).
How many amps does 1,000 watts draw at 120 volts?
At 120 volts, 1,000 watts draws approximately 8.33 amps (1000 / 120 = 8.33). This is well within the capacity of a standard 15-amp or 20-amp household circuit.
Why do electricians need to convert watts to amps?
Electricians convert watts to amps to properly size circuit breakers, wire gauges, and conduit. Circuit breakers are rated in amps, not watts, so knowing the amperage draw of connected loads is essential for safe circuit design and NEC compliance.