Amps to kW Calculator
Enter the current in amps, voltage, and the appropriate electrical system. For AC circuits, you can also enter the power factor to obtain a more realistic real-power result.
The calculator supports DC, single-phase AC, and three-phase AC systems, because the relationship between current and power changes depending on the type of circuit.
Amps to kW Calculator
Convert electrical current in amps to kilowatts using the voltage, phase type, and power factor that match your system.
kW = Amps × Volts ÷ 1000
kW = Amps × Volts × PF ÷ 1000
kW = √3 × Amps × Volts × PF ÷ 1000
What does amps to kW actually mean?
Amps and kilowatts describe different things.
Amps (A) measure electrical current.
Volts (V) measure electrical potential difference.
Kilowatts (kW) measure real electrical power.
That means there is no single universal answer to a question such as “How many kW is 20 amps?” The voltage must also be known, and AC loads may require a power-factor adjustment.
For example, 20 A at 240 V on a single-phase circuit with a power factor of 1 produces:
20 × 240 × 1 ÷ 1000 = 4.8 kW
The same 20 amps at a different voltage would produce a different power value.
Choose the electrical system before converting
The first question is not simply how many amps you have. It is what type of electrical supply those amps belong to.
DC amps to kW
For a DC circuit, the calculation is straightforward:
kW = Amps × Volts ÷ 1000
For example, a 40 A DC load at 120 V is:
40 × 120 ÷ 1000 = 4.8 kW
No power-factor multiplier is required for this basic DC calculation.
Single-phase AC amps to kW
For a single-phase AC circuit:
kW = Amps × Volts × Power Factor ÷ 1000
If the load is purely resistive, such as a simple heating element, the power factor can be close to 1.
Example:
30 A × 240 V × 1.00 ÷ 1000 = 7.2 kW
For a motor or other inductive load, using the actual power factor can make the calculation more representative of real power.
Three-phase amps to kW
Balanced three-phase systems use a different relationship.
When using line-to-line voltage:
kW = √3 × Amps × Volts × Power Factor ÷ 1000
Since √3 is approximately 1.732, the formula can also be written as:
kW = 1.732 × Amps × Volts × Power Factor ÷ 1000
For example, 50 A at 400 V three-phase with a power factor of 0.90 gives approximately:
1.732 × 50 × 400 × 0.90 ÷ 1000 = 31.18 kW
The three-phase calculation assumes the appropriate line voltage and a balanced system.
Why voltage matters so much
A common mistake is to think that amps can be converted directly into kilowatts.
They cannot.
Current describes the flow of charge, while power depends on both current and voltage. Increasing the voltage while keeping the current constant increases the calculated power.
Consider 10 amps:
10 A at 120 V = 1.2 kW at PF 1
10 A at 230 V = 2.3 kW at PF 1
10 A at 240 V = 2.4 kW at PF 1
10 A at 400 V three-phase = approximately 6.93 kW at PF 1
The last example is different because three-phase power includes the √3 factor.
This is why an amps-to-kW calculation should always include the electrical system and voltage rather than relying on a fixed conversion table.
What is power factor?
Power factor, usually written as PF, describes the relationship between real power and apparent power in an AC circuit.
A purely resistive load can have a power factor close to 1.00. Motors, compressors, transformers, and other inductive equipment can have a lower power factor.
For example, if a 240 V single-phase load draws 20 A:
With PF = 1.00:
20 × 240 × 1.00 ÷ 1000 = 4.80 kW
With PF = 0.80:
20 × 240 × 0.80 ÷ 1000 = 3.84 kW
So using a power factor of 1 for every AC appliance can overestimate real power.
Whenever the equipment nameplate or manufacturer documentation provides a power factor, use that figure instead of guessing. Typical values can vary considerably between equipment types and operating conditions.
Amps to kW calculator examples
Here are a few common examples using a power factor of 1 for single-phase calculations.
| Current | Voltage | Phase | Power factor | Approx. power |
|---|---|---|---|---|
| 5 A | 120 V | Single-phase | 1.00 | 0.60 kW |
| 10 A | 120 V | Single-phase | 1.00 | 1.20 kW |
| 15 A | 240 V | Single-phase | 1.00 | 3.60 kW |
| 20 A | 240 V | Single-phase | 1.00 | 4.80 kW |
| 30 A | 240 V | Single-phase | 1.00 | 7.20 kW |
| 50 A | 240 V | Single-phase | 1.00 | 12.00 kW |
| 100 A | 240 V | Single-phase | 1.00 | 24.00 kW |
These values are mathematical conversions, not recommendations for breaker, cable, generator, or equipment sizing.
When an amps-to-kW calculator is useful
An amps-to-kW calculation can be useful when checking electrical loads, interpreting equipment specifications, comparing power requirements, estimating generator loads, or translating a current measurement into a more familiar power unit.
It can also be useful when a piece of equipment gives its electrical demand in amps while another specification is expressed in kilowatts.
However, calculated power should not be confused with a complete electrical design calculation. Starting current, duty cycle, load diversity, efficiency, harmonics, conductor limitations, protective-device requirements, and local electrical codes can all matter in real installations.
Amps to kW calculator formula at a glance
Keep these three formulas handy:
DC
kW = A × V ÷ 1000
Single-phase AC
kW = A × V × PF ÷ 1000
Three-phase AC
kW = √3 × A × V × PF ÷ 1000
For three-phase calculations using line-to-line voltage, √3 is approximately 1.732.