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Amps to Watts Calculator

Convert electrical current (Amps) to power (Watts). Supports DC, AC Single-Phase, and AC Three-Phase circuits.

Circuit Details

Result

Power

1,200 W

(1.2 kW)

Formula Used

P = V × I

Amps to Watts Conversion Guide

Understanding the relationship between electric current (amps) and power output (watts) is crucial for home electrical safety, DIY projects, and choosing the right generator or circuit breakers. The calculation relies on Ohm's Law, which links electrical current, voltage, and power.

DC Circuits

For direct current (DC) systems (like car batteries or solar panels), the math is straightforward. Power in watts is calculated by multiplying the voltage by the current in amperes:
P = V × IWhere P is power in watts, V is voltage in volts, and I is current in amps.

AC Single-Phase

For standard alternating current (AC) single-phase systems (like typical home wall outlets), you must account for the efficiency of the device, represented by the Power Factor (PF). Power factor ranges from 0 to 1, where 1 is a perfectly resistive load (like a heater or incandescent bulb) and lower values are inductive loads (like electric motors, refrigerators, or computers):
P = V × I × PF

AC Three-Phase

Three-phase systems are commonly used in industrial settings to deliver higher power. The formula changes depending on whether you measure line-to-line or line-to-neutral voltage:

  • Line-to-Line Voltage (VLL): Used when measuring between any two of the three active lines:P = √3 × V × I × PF ≈ 1.732 × V × I × PF
  • Line-to-Neutral Voltage (VLN): Used when measuring between one active line and the neutral line:P = 3 × V × I × PF

How to Calculate Watts from Amps — Step-by-Step

Follow these easy steps to manually convert amps to watts for any household appliance:

  1. Find the Ampere Rating: Look at the label or nameplate on the back of the device. It will say something like "Current: 10A" or "10 Amps".
  2. Identify the Voltage: Standard home outlets in the United States and Canada operate at 120 volts, while European and Asian outlets operate at 220–240 volts.
  3. Multiply Amps by Volts: For a basic estimation (assuming a power factor of 1), multiply the current by the voltage. For example, a 10A toaster plugged into a 120V outlet draws:10 Amps × 120 Volts = 1,200 Watts

Common Appliance Wattage Reference Chart (at 120V)

ApplianceCurrent (Amps)Estimated Wattage (Watts)
Smartphone Charger0.1A - 0.2A12W - 24W
LED TV0.8A - 1.5A100W - 180W
Refrigerator3A - 6A360W - 720W
Microwave Oven8A - 12A960W - 1,440W
Hair Dryer12A - 15A1,440W - 1,800W

Frequently Asked Questions (FAQ)

Can a 15-amp breaker handle 2,000 watts?

No, not continuously. A standard 15-amp circuit breaker at 120V has a maximum safety capacity of 1,800 watts (15A × 120V). For continuous loads (running for 3 hours or more), safety codes recommend keeping the load below 80%, which is 1,440 watts.

Is current (amps) the same as power (watts)?

No. Current (amperes) measures the volume of electron flow through a wire, similar to the volume of water flowing through a pipe. Power (watts) measures the total work done per second, combining both the volume of flow (amps) and the pressure pushing it (voltage).

How does power factor affect single-phase AC calculations?

The power factor represents how efficiently current is converted into useful work. Inductive devices (with coils, compressors, or motors) draw extra "reactive" current that doesn't do work, lowering the power factor. This means you need more amps to deliver the same watts compared to a resistive heater.