Convert watts to amps for any voltage. Enter wattage and voltage to find current draw for circuit sizing, breaker selection, and wire gauge planning.
Converting watts to amps is essential for determining what circuit, breaker, and wire size an electrical load requires. While watts tell you how much power a device uses (and therefore your energy cost), amps determine the physical infrastructure needed: conductor size, overcurrent protection, and switch ratings.
The fundamental formula is Amps = Watts ÷ (Volts × Power Factor). For resistive loads like heaters and incandescent bulbs, the power factor is 1.0, simplifying the formula to Amps = Watts ÷ Volts. For motor-driven and electronic loads, the power factor (typically 0.75–0.95) means the actual current draw is higher than the simple W/V calculation.
This calculator converts watts to amps at any voltage, with optional power factor for AC circuits. It's used by electricians, homeowners, and engineers for circuit design, generator sizing, and load balancing.
Integrating this calculation into regular energy reviews ensures that conservation strategies are grounded in measured data rather than assumptions about building performance and usage patterns.
Knowing the amp draw of a load is critical for selecting the right breaker, wire size, and outlet type. This calculator converts known wattage to amps at your specific voltage, ensuring safe and code-compliant installations. Data-driven tracking enables proactive energy management, helping organizations reduce operational costs while progressing toward environmental sustainability goals and carbon reduction targets.
Amps = Watts ÷ (Volts × Power Factor)
Result: 12.5 A
A = 1,500 ÷ (120 × 1.0) = 12.5 amps. A 1,500W heater on a 120V circuit draws 12.5A. This requires at minimum a 15A circuit, though a 20A circuit is recommended for a continuous load.
14 AWG copper: 15A max at 60°C. 12 AWG: 20A. 10 AWG: 30A. 8 AWG: 40A. 6 AWG: 55A. Long runs require upsizing to compensate for voltage drop. For runs over 50 feet, consider using the next larger gauge.
100W = 0.83A. 500W = 4.17A. 1,000W = 8.33A. 1,500W = 12.5A. 1,800W = 15A (max for 15A circuit). 2,400W = 20A (max for 20A circuit). These assume PF = 1.0 (resistive loads).
The National Electrical Code requires circuit conductors be rated for the maximum overcurrent device (breaker) protecting them. Continuous loads must not exceed 80% of the breaker rating. This means a 20A breaker supports 16A continuous — or 1,920W at 120V.
At 120V: 1,500 ÷ 120 = 12.5 amps. At 240V: 1,500 ÷ 240 = 6.25 amps. The 120V version draws twice the current and needs a larger circuit. Most 1,500W portable heaters use 120V.
Calculate amps (W ÷ V), then choose a breaker rated above that value. For continuous loads, the breaker must be rated at 125% of the load current. A 12.5A continuous load needs a 16A minimum breaker — use a 20A.
Power (watts) equals volts times amps. If voltage doubles, amps are halved for the same wattage. This is why high-power appliances use 240V — the lower current allows smaller, cheaper wires and breakers.
A lower power factor means the device draws more amps than W/V suggests. For example, 1,000W at 120V with PF = 0.80 draws 10.4A, not 8.3A. The extra current doesn't do useful work but still heats wires and loads breakers.
Check the nameplate label (usually on the back or bottom) for watts or amps and volts. If only amps and volts are listed, multiply them for VA (apparent power). For the wattage, you'd also need the power factor.
Yes, as long as the total amp draw doesn't exceed the circuit rating (80% for continuous loads). Add up all device amps. For example, a 15A circuit can handle a 8A + 5A combination (13A total) but not three 8A devices (24A total).