How Many Watts is 5 Amps? 120V, 230V & 3-Phase Conversion Chart

At a standard US household voltage of 120V, 5 amps is exactly 600 watts. At a standard European or UK voltage of 230V, 5 amps equals 1,150 watts. The foundational DC and single-phase AC resistive formula is P = I × V. Substituting our exact values for a North American circuit yields: 600W = 5A × 120V. However, treating this single calculation as a universal truth is a fast track to tripped breakers or undersized wire, because the true wattage shifts dramatically depending on your supply voltage, phase configuration, and the power factor of the load.

The Core Conversion: 5 Amps to Watts Across Standard Voltages

To size a breaker or select the right AWG wire, you need to know the actual power dissipation. The table below maps exactly what 5 amps translates to in watts across the most common global and industrial voltage standards. These calculations assume a purely resistive load (Power Factor = 1.0), such as incandescent lighting, strip heaters, or basic switching power supplies operating at peak efficiency.

Neighboring Current Values: 4A to 6A Quick Reference

On the bench, you rarely see a load draw exactly 5.00 amps. Multimeter readings fluctuate with line voltage sags and thermal drift. Here is a ±20% reference window (4A to 6A) for the two most common single-phase residential voltages. This is particularly useful when calculating voltage drop or checking if a 15A branch circuit is approaching its 80% continuous load limit (12A max).

When the Math Breaks: Power Factor and 3-Phase Shifts

The simple P = I × V formula works perfectly for DC circuits and purely resistive AC loads. But the moment you introduce inductive or capacitive components—like AC induction motors, transformers, or cheap switch-mode power supplies—the conversion becomes meaningless unless you account for Power Factor (PF).

Power factor is the ratio of real power (Watts, which does the actual work and generates heat) to apparent power (Volt-Amps, VA, which the utility must supply). According to the All About Circuits AC power guide, if you measure 5 amps on a 120V circuit powering an older, uncorrected AC motor with a PF of 0.75, your actual wattage is not 600W. It is 450W (120V × 5A × 0.75). The remaining 150VA is reactive power bouncing back and forth in the magnetic field. If you try to size a solar inverter or UPS based on the 600W figure without knowing the PF, you will severely undersize the system's current capacity.

For three-phase systems, the math shifts again. You must multiply by the square root of 3 (≈1.732). The formula becomes P = √3 × V × I × PF. This is why 5 amps on a 208V 3-phase supply yields 1,801 watts, not the 1,040 watts you would get if you mistakenly used the single-phase formula.

Real-World Sizing: Breakers, Continuous Loads, and Wire Gauge

Knowing that 5 amps equals 600 watts at 120V tells you the power, but it doesn't tell you how to protect the circuit. Under NFPA 70 (National Electrical Code) guidelines, breaker sizing depends on whether the 5A load is continuous (running for 3 hours or more) or non-continuous.

• Non-Continuous Loads: A 5A load requires a breaker rated for at least 5A. In standard US residential panels, the smallest common branch breaker is 15A. 14 AWG copper wire (rated 15A at 60°C) is perfectly adequate.
• Continuous Loads: NEC Article 210.20 requires continuous loads to be derated to 80% of the breaker's capacity. A 5A continuous load requires a breaker rated for at least 6.25A (5A × 1.25). A standard 15A breaker still easily covers this, and 14 AWG NM-B or THHN wire remains the correct choice.

For low-voltage DC applications (like a 5A draw on a 12V LiFePO4 battery system), NEC mains rules don't strictly apply, but voltage drop and fire safety do. A 5A continuous draw on an undersized 22 AWG breadboard jumper wire will melt the insulation. For 12V DC at 5A over a short run (under 3 feet), 16 AWG wire is sufficient. For longer runs to a solar charge controller or inverter, step up to 12 AWG or 10 AWG to minimize I²R heating losses and keep the voltage drop below 3%.