3-Phase Power Calculator: kW to Amps, Amps to kW (2026)

Three-phase power runs most commercial buildings, larger motors and big HVAC equipment. Its formulas carry an extra factor, the square root of 3, because the three phases peak at different moments and share the load.

For three-phase power, amps = kW × 1,000 ÷ (volts × 1.732 × power factor). At 480 volts and a power factor of 0.85, 10 kW draws about 14.2 amps, and 50 amps delivers about 35.3 kW.

The formulas

With line-to-line voltage V, line current I and power factor PF:

• Apparent power (kVA) = V × I × √3 ÷ 1,000
• Real power (kW) = V × I × √3 × PF ÷ 1,000
• Amps from kW = kW × 1,000 ÷ (V × √3 × PF)
• Amps from kVA = kVA × 1,000 ÷ (V × √3)

√3 is about 1.732. The calculator also accepts phase values instead of line values, and shows reactive power, horsepower and energy over time.

Quick reference: kW to amps

These assume a power factor of 0.85, typical of motor loads. For purely resistive loads such as heaters (power factor 1.0), the current is 15% lower: 10 kW at 480 volts draws 12.0 amps.

Power factor

Power factor is the share of the current that does useful work. Heaters run near 1.0; motors and some electronics run lower, because part of their current flows back and forth without doing work. A lower power factor means more current for the same real power, which sets the size of wires and breakers.

Wye and delta

• Wye (Y): each phase connects between a line and a shared neutral. Line voltage = √3 × phase voltage, and line current = phase current. A 208Y/120 system gives 120 volts from each line to neutral.
• Delta (Δ): each phase connects between two lines. Line voltage = phase voltage, and line current = √3 × phase current.

The calculator converts between line and phase values for either connection.

Single-phase vs. three-phase

Most homes are served single-phase, 120/240 volts. For the same power, three-phase uses less current per conductor: 10 kW at 240 volts and a power factor of 1.0 draws 41.7 amps single-phase but 24.1 amps three-phase. That's why large equipment and commercial buildings use it.

Motors and horsepower

One horsepower is 745.7 watts (NIST). A motor's electrical input is higher than its shaft output by its efficiency: a 10 hp motor delivering full output at 90% efficiency draws about 8,286 watts. For sizing conductors and protection, electricians use the motor full-load current tables in the National Electrical Code (Table 430.250 for three-phase motors), not the nameplate output alone.

Frequently asked questions

How many amps is 10 kW three-phase?

About 14.2 amps at 480 volts, 28.3 at 240 and 32.7 at 208, at a power factor of 0.85. At a power factor of 1.0 the current is 15% lower.

How do I convert amps to kW for three-phase?

kW = volts × amps × 1.732 × power factor ÷ 1,000. 50 amps at 480 volts and 0.85 is about 35.3 kW.

Why is the square root of 3 in three-phase formulas?

The three phases are 120 degrees apart, so the voltage between two lines is √3 times the voltage of one phase.

What's the difference between kW and kVA?

kVA is apparent power, volts times amps. kW is the real power that does work: kVA times the power factor.