Engineering

Amps to kW Calculator

Convert amps to kilowatts for DC, AC single-phase, and AC three-phase circuits. Enter current, voltage, phase type, and power factor to calculate real power in kW, watts, apparent power in kVA, estimated horsepower, and energy use in kWh.

amps-to-kw
Real power
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Watts—
Apparent power—
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Estimated horsepower—
Energy for runtime—
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Amps to kW formula

The amps to kW conversion depends on the type of electrical system. Amps measure current, volts measure electrical pressure, and kilowatts measure real power. For a useful conversion, you must know the voltage. For AC systems, you should also know the power factor.

DC: kW = A × V ÷ 1,000 AC single-phase: kW = A × V × PF ÷ 1,000 AC three-phase using line-to-line voltage: kW = √3 × A × V(L-L) × PF ÷ 1,000 AC three-phase using line-to-neutral voltage: kW = 3 × A × V(L-N) × PF ÷ 1,000

Which formula should you use?

System Use when Formula
DC Batteries, solar DC strings, DC power supplies kW = A × V ÷ 1,000
AC single-phase Home circuits, small appliances, single-phase motors kW = A × V × PF ÷ 1,000
AC three-phase L-L Most 3-phase nameplate voltages: 208, 400, 415, 480 V kW = √3 × A × V × PF ÷ 1,000
AC three-phase L-N When voltage is measured from phase to neutral kW = 3 × A × V × PF ÷ 1,000
Amps + ohms Resistance is known instead of voltage kW = A² × Ω ÷ 1,000

Common amps to kW examples

These examples use power factor 1 unless otherwise stated. For motors and other inductive loads, use the actual power factor from the nameplate when available.

Example Calculation Result
10 amps at 120 V single-phase 10 × 120 ÷ 1,000 1.20 kW
20 amps at 230 V single-phase 20 × 230 ÷ 1,000 4.60 kW
30 amps at 240 V single-phase 30 × 240 ÷ 1,000 7.20 kW
50 amps at 48 V DC 50 × 48 ÷ 1,000 2.40 kW
20 amps at 400 V 3-phase, PF 1 √3 × 20 × 400 ÷ 1,000 13.86 kW
50 amps at 415 V 3-phase, PF 0.85 √3 × 50 × 415 × 0.85 ÷ 1,000 30.55 kW
100 amps at 480 V 3-phase, PF 0.8 √3 × 100 × 480 × 0.8 ÷ 1,000 66.51 kW

Amps to kW chart at common voltages

This quick chart helps answer common searches such as 10 amps to kW, 20 amps to kW, 30 amps to kW, 100 amps to kW, and 200 amps to kW. Single-phase values assume PF 1. Three-phase values use line-to-line voltage and PF 1.

Amps 120 V 1φ 230 V 1φ 240 V 1φ 400 V 3φ 415 V 3φ 480 V 3φ
5 A 0.60 kW 1.15 kW 1.20 kW 3.46 kW 3.59 kW 4.16 kW
10 A 1.20 kW 2.30 kW 2.40 kW 6.93 kW 7.19 kW 8.31 kW
15 A 1.80 kW 3.45 kW 3.60 kW 10.39 kW 10.78 kW 12.47 kW
20 A 2.40 kW 4.60 kW 4.80 kW 13.86 kW 14.38 kW 16.63 kW
30 A 3.60 kW 6.90 kW 7.20 kW 20.78 kW 21.56 kW 24.94 kW
40 A 4.80 kW 9.20 kW 9.60 kW 27.71 kW 28.75 kW 33.26 kW
50 A 6.00 kW 11.50 kW 12.00 kW 34.64 kW 35.94 kW 41.57 kW
60 A 7.20 kW 13.80 kW 14.40 kW 41.57 kW 43.13 kW 49.88 kW
100 A 12.00 kW 23.00 kW 24.00 kW 69.28 kW 71.88 kW 83.14 kW
150 A 18.00 kW 34.50 kW 36.00 kW 103.92 kW 107.82 kW 124.71 kW
200 A 24.00 kW 46.00 kW 48.00 kW 138.56 kW 143.76 kW 166.28 kW

For AC loads with a power factor below 1, multiply the chart value by the power factor. Example: 20 A at 400 V three-phase is 13.86 kW at PF 1, or 11.09 kW at PF 0.8.

Power factor guide for amps to kW

Power factor changes the difference between apparent power and real power. If a load has 10 kVA of apparent power and a 0.8 power factor, the real power is 8 kW. Resistive loads are often close to PF 1, while motors and magnetic loads are usually lower.

Load type Typical PF range Notes
Electric heater / resistive oven 0.95 – 1.00 Usually close to real power
Incandescent lamp 1.00 Mostly resistive
Induction motor at load 0.75 – 0.90 Use motor nameplate for accuracy
Lightly loaded motor 0.20 – 0.70 PF can be much lower at low load
Fluorescent / discharge lighting 0.50 – 0.95 Depends on ballast and correction
UPS / inverter loads 0.70 – 1.00 Depends on equipment design

Worked example: 50 amps to kW on a 415 V three-phase motor

Given: Current = 50 A Voltage = 415 V line-to-line Power factor = 0.85 System = three-phase AC Formula: kW = √3 × A × V × PF ÷ 1,000 Calculation: kW = 1.732 × 50 × 415 × 0.85 ÷ 1,000 kW = 30.55 kW

If the motor efficiency is 90%, the estimated useful output is 30.55 × 0.90 = 27.50 kW, which is about 36.9 horsepower. The electrical input kW is still 30.55 kW; efficiency only estimates how much of that input becomes useful shaft output.

kW vs kWh vs kVA

These three terms are related but not the same. kW is real power at a moment. kWh is energy over time. kVA is apparent power in AC systems before applying power factor.

kW = real power kWh = kW × hours kVA = apparent power kW = kVA × PF PF = kW ÷ kVA

For example, a 5 kW load running for 8 hours uses 40 kWh. A 10 kVA generator feeding a load at 0.8 PF supplies 8 kW of real power.

Common mistakes when converting amps to kW

Using amps alone: amps cannot be converted to kW without voltage. Ignoring power factor: AC motors may use less real kW than a simple volts × amps calculation suggests. Mixing line-to-line and line-to-neutral voltage: this is a common three-phase mistake. Confusing kW with kWh: kW is power, while kWh is energy after multiplying by time.

Common questions

  • To convert amps to kW, multiply amps by volts, then divide by 1,000. For DC and resistive single-phase loads, the simple formula is kW = amps × volts ÷ 1,000. For AC loads with a power factor, multiply by the power factor as well. For three-phase line-to-line voltage, use kW = √3 × amps × volts × power factor ÷ 1,000.
  • For DC circuits, the formula is kW = A × V ÷ 1,000. For example, 50 amps at 48 volts is 50 × 48 ÷ 1,000 = 2.4 kW. DC calculations do not use power factor because there is no alternating-current phase angle.
  • For single-phase AC circuits, use kW = A × V × PF ÷ 1,000. PF is power factor. If the load is purely resistive, such as a heater, PF is usually close to 1. If the load is a motor or compressor, PF is often lower, so using 1 may overestimate the real kilowatts.
  • For three-phase AC using line-to-line voltage, use kW = √3 × A × V × PF ÷ 1,000. For three-phase using line-to-neutral voltage, use kW = 3 × A × V × PF ÷ 1,000. Most three-phase nameplates and supply voltages are given as line-to-line voltage, such as 208 V, 400 V, 415 V, or 480 V.
  • Balanced three-phase systems have three AC waveforms separated by 120 degrees. When line-to-line voltage is used, the geometry of those phase relationships introduces the √3 factor in the real power formula. That is why a three-phase 400 V, 20 A circuit carries more power than a single-phase 400 V, 20 A circuit at the same power factor.
  • Yes. Amps measure current, while kW measures power. Current alone is not enough because 10 amps at 12 volts is only 0.12 kW, while 10 amps at 240 volts is 2.4 kW before power factor. Always include the circuit voltage when converting amps to kilowatts.
  • You need power factor for AC real power calculations. DC circuits do not use power factor. AC heaters and incandescent lamps are usually close to PF 1. Motors, compressors, transformers, and fluorescent lighting often have lower power factors, so entering the correct PF gives a more realistic kW result.
  • Use PF 1.0 for a mostly resistive load such as a heater. For motors, 0.8 to 0.9 is commonly used for a rough estimate when the actual nameplate value is unknown. For accurate design, billing, generator sizing, or protection work, use the power factor listed on the equipment nameplate or measured with a power meter.
  • For DC or single-phase PF 1, 100 amps at 240 volts is 24 kW because 100 × 240 ÷ 1,000 = 24. If the load is single-phase AC at PF 0.8, it is 19.2 kW. For three-phase 240 V line-to-line at PF 1, it is about 41.57 kW.
  • For DC or single-phase PF 1, 30 amps at 240 volts is 7.2 kW. With a power factor of 0.8, the real power is 5.76 kW. For a three-phase 240 V line-to-line circuit at PF 0.8, the result is about 9.98 kW.
  • Amps in 1 kW depends on voltage, phase, and power factor. At 120 V single-phase PF 1, 1 kW is 8.33 A. At 230 V single-phase PF 1, 1 kW is 4.35 A. At 400 V three-phase line-to-line PF 1, 1 kW is about 1.44 A.
  • No. kW is real power, the power that does useful work. kVA is apparent power, the combination of real and reactive power in an AC circuit. The relationship is kW = kVA × power factor. If PF is 1, kW and kVA are numerically equal. If PF is 0.8, 10 kVA equals 8 kW.
  • Yes, but you need time. First convert amps to kW, then multiply by hours. Formula: kWh = kW × hours. For example, a 2.4 kW load running for 5 hours uses 12 kWh. This calculator includes an optional runtime field to estimate energy use in kWh.
  • Use the voltage type that matches your data. If your supply is described as 400 V, 415 V, 480 V, or 208 V three-phase, that is usually line-to-line voltage. If you are using phase-to-neutral voltage, such as 230 V in a 400/230 V system, choose line-to-neutral.
  • Yes, it can estimate the electrical input kW for a motor if you enter the motor current, voltage, phase, and power factor. If you also enter efficiency, the calculator estimates useful output kW and horsepower. For final motor sizing or breaker selection, use the motor nameplate and local electrical code requirements.
  • The math is accurate when the inputs are accurate. The biggest sources of error are using the wrong voltage type, assuming the wrong power factor, ignoring motor efficiency, or using running current when the actual load changes. For estimates, the result is useful. For engineering, billing, or safety-critical work, verify the values from a nameplate or meter.