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kW to Amps Calculator
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Watts to Amperes Calculator

Input your power in watts and system voltage to find the current flow. Ideal for lighting systems, small home appliances, and low-power electronics.

Circuit Parameters

Watts → Amps

DECIMALS
3
Calculated Current
— A

Safe current levels help prevent wire overheating.

In kW —
In Milliamps —

The Conversion Formula

Watts to amps conversion requires knowing the circuit voltage — and power factor for AC systems.

DC Systems
I = W ÷ V

The simplest form of Ohm's Law — divide watts by volts to get amps in any DC circuit.

1-Phase AC
I = W ÷ (V × PF)

AC loads with a power factor below 1.0 draw more current than their watt rating suggests — accounting for the reactive component.

3-Phase AC
I = W ÷ (√3 × V × PF)

Three-phase systems distribute power across three phases — the √3 factor is mandatory for line-to-line voltage conversions.

How to Convert Watts to Amps

The watts-to-amps conversion is one of the most frequently used calculations in electrical work — from selecting the right fuse for an electronics project to sizing a circuit breaker for a household appliance. Watts measure real power consumed; amps measure the current flowing through the conductor. You need voltage (and power factor for AC) to bridge the two.

Watts vs. VA: What's the Difference?

Watts (W) measure real power — the energy actually converted to heat, light, or motion. Volt-Amperes (VA) measure apparent power — what the source must supply, including reactive current. For resistive loads (heaters, incandescent bulbs) they're equal. For inductive loads (motors, transformers), VA is always higher than watts.

Common Household Examples

  • 1500W Space Heater at 120V DC: 1500 ÷ 120 = 12.5A. Needs a 15A circuit at minimum.
  • 800W Microwave at 120V AC (PF 0.95): 800 ÷ (120 × 0.95) ≈ 7.0A. Comfortably fits a 15A circuit.
  • 3000W Dryer at 240V AC (PF 1.0): 3000 ÷ 240 = 12.5A — typically wired on a 30A circuit to allow for startup transients.

Step-by-Step Conversion

  1. Find the Wattage: Check the device label, user manual, or measured consumption with a watt meter.
  2. Confirm the Voltage: Use the outlet voltage — 120V or 240V in North America; 230V in Europe.
  3. Apply the Power Factor: Use 1.0 for pure resistive loads (heaters, light bulbs). Use 0.8–0.9 for motors and most AC equipment.
  4. Size Your Protection: The calculated amps is the continuous draw. Size breakers and fuses at 125% of continuous load per NEC requirements.
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