Line Voltage (V) Enter the line-to-line voltage in volts (e.g., 415)

Line Current (A) Enter the line current in amperes (e.g., 50)

Power Factor (unitless) Enter the power factor from 0 to 1 (e.g., 0.85 for most motors)

System Type (configuration) 3-Phase Delta (3-Wire) 3-Phase Wye (4-Wire) Select your three-phase wiring configuration

Quick Examples:

Industrial Motor Load Commercial Building Load

Calculate Clear

This calculator is for informational purposes only. Verify results with appropriate professionals for important decisions.

What Is Three-Phase Power

Three-phase power is the total real power used by an electrical system that has three alternating currents. It is the useful power that does actual work, like running motors or heating elements. Unlike apparent power, which includes wasted energy, three-phase power only counts the energy that turns into heat, motion, or light. It is measured in kilowatts (kW). Three-phase systems are common in factories and large buildings because they move power more efficiently than single-phase systems.

How Three-Phase Power Is Calculated

Formula

The formula starts by multiplying the square root of 3 by the line voltage and line current. This gives the apparent power in volt-amps. Then, the power factor scales that number down to show only the real, useful power. The power factor is a number between 0 and 1 that tells you how much of the total power is actually doing work. A power factor of 1 means all the power is useful. A lower number means some power is wasted. Finally, dividing by 1,000 converts the result from watts to kilowatts for easier reading.

Why Three-Phase Power Matters

Knowing the three-phase power helps you pick the right size wires, breakers, and generators. If you guess wrong, your equipment may overheat or fail. This number gives you a clear starting point for safe and efficient electrical design.

Why Accurate Power Calculations Are Important for Electrical Safety

If you underestimate three-phase power, wires can overheat and start a fire. Breakers may trip often or fail to trip when they should. If you overestimate, you may spend too much on oversized equipment. Using the correct voltage, current, and power factor helps you avoid these problems and keeps your electrical system safe and reliable.

For Equipment Sizing

When you need to buy a generator, transformer, or breaker, the three-phase power number tells you the minimum rating you should look for. You may consider adding a safety margin of about 20 percent above your calculated value. This helps handle short surges in power without tripping the breaker or overloading the generator.

For Load Verification

If you want to check whether an existing panel or feeder can handle a new load, compare your calculated three-phase power to the rated capacity of the equipment. If your result is close to the limit, you may consider upgrading the panel or spreading the load across more circuits to avoid overloading.

For Nonlinear Loads

This formula assumes a steady, balanced load with a clean sine wave. If your system has variable frequency drives, LED lighting, or other nonlinear loads, the actual power may differ from this estimate. You may consider using a power quality meter to measure real power directly for the most accurate result.

Three-Phase Power vs Apparent Power

Three-phase power (kW) is the real, useful power that does work. Apparent power (kVA) is the total power supplied by the source. The difference between them is reactive power (kVAR), which flows back and forth without doing useful work. A common mistake is sizing equipment based on kW alone. Most electrical equipment is rated in kVA, so you should use apparent power for sizing.