100 Watts to Amps — How Many Amps Is 100 Watts?
100 Watts equals 0.83 amps at 120V or 0.42 amps at 240V. Common 100W devices: LED bulb, USB charger, small fan.
100 Watts Amps at Every Voltage
| Voltage | Single Phase | Three Phase |
|---|---|---|
| 120V | 0.83A | 0.48A |
| 208V | 0.48A | 0.28A |
| 240V | 0.42A | 0.24A |
| 277V | 0.36A | 0.21A |
| 480V | 0.21A | 0.12A |
The Formula
Single Phase: Amps = Watts ÷ Volts. For 100 Watts at 120V: 100 ÷ 120 = 0.83A.
Three Phase: Amps = Watts ÷ (Volts × 1.732). For 100 Watts at 240V 3-phase: 100 ÷ (240 × 1.732) = 0.24A.
With power factor: Amps = Watts ÷ (Volts × PF). A PF of 0.8 increases the current draw by 25%.
Wire and Breaker for 100 Watts at 120V
At 120V, 100 Watts draws 0.8A. Recommended: 14 AWG copper wire with a 15A breaker per NEC 310.16. For continuous loads (3+ hours), apply 125% rule. Use our Wire Size Calculator for exact sizing.
Common 100W Devices
LED bulb, USB charger, small fan. Always check the device nameplate for exact wattage — rated watts may differ from actual consumption.
Disclaimer: Calculations are for reference. Verify with device nameplate. Consult a licensed electrician for installations.