KW To Amps Calculator
Converting kilowatts to amps is one of the most common electrical calculations, and the formula changes with the current type. DC is a straight division, single-phase AC adds the power factor, and three-phase AC adds the √3 phase factor on top. Get the wrong one and you undersize a breaker or a cable.
The calculator below handles all three current types in both directions, kilowatts to amps and amps to kilowatts, with voltage presets, power factor presets by equipment type, an apparent power (kVA) readout, and the exact formula it used, with your numbers in it.
kW to Amps Calculator
DC, single-phase, and three-phase conversions in both directions, with voltage and power-factor presets.
–
| Apparent power | – |
| Formula used | – |
Quick Answer
A 50 kW three-phase load at 400 V with a 0.8 power factor draws 90.21 A, with an apparent power of 62.50 kVA. For a continuous load, the sizing figure at 125% is 112.76 A. The calculator above is pre-filled with this exact run; change the current type to DC or single-phase and the same 50 kW needs a very different current.
Key takeaways
- There is no single amps figure for a kilowatt. Voltage, phase count and (for AC) power factor all move the answer, which is why 1 kW can mean 5.43 A or 1.60 A.
- Three-phase voltage here is line-to-line. Entering a line-to-neutral figure instead is the most common way this calculation goes wrong.
- In DC mode the power factor field is ignored completely: the tool forces it to 1, so even a typed value above 1 produces a normal DC result instead of an error.
- The result is a running current under ideal conditions. Breaker and cable sizing still needs the 125% continuous-load rule, the nameplate figure, and local code.
- Quick Answer
- How to use the kW to amps calculator
- The three formulas, and their reverses
- Worked examples for every current type and voltage
- Picking a power factor that does not wreck the answer
- From calculated amps to breakers and cable
- What this calculation leaves out
- What competing calculators miss
- Frequently asked questions
- Add This Calculator to Your Website
- References
How to use the kW to amps calculator
Pick the direction first, then the current type, then fill in the numbers. Results stay hidden until you click Convert.
- Direction: kW → Amps when you know the load and need its current; Amps → kW when you measured a current and want the power. Switching direction relabels the first field and hides the old result, but it keeps the values you typed, so check them before converting.
- Current type: DC, single-phase AC or three-phase AC. This choice changes the formula, not just the label.
- Power or current: kilowatts in forward mode, amps in reverse mode. Both must be greater than zero.
- Voltage: type it or tap a preset (120, 208, 230, 240, 400, 480). For three-phase, this is the line-to-line voltage.
- Power factor: AC only. Type it or tap an equipment preset. It must sit between 0 and 1; the tool rejects anything above 1 in AC modes. For DC the field disappears and anything in it is ignored.
If your starting point is amps and volts on a simpler DC or resistive job, the amp to watt calculator covers that two-value version. This page is the fuller one: it adds phase count, power factor and the trip back from amps to kilowatts.
The three formulas, and their reverses
Every conversion starts by turning kilowatts into watts (kW × 1000). What divides those watts depends on the circuit.
Single-phase AC: I = P ÷ (V × PF)
Three-phase AC: I = P ÷ (√3 × V × PF)
Reverse, DC: P = I × V ÷ 1000
Reverse, single-phase: P = I × V × PF ÷ 1000
Reverse, three-phase: P = √3 × I × V × PF ÷ 1000
Apparent power: kVA = kW ÷ PF for AC; for DC, kVA equals kW
The power factor is there because AC loads do not use every amp they draw: part of the current cycles back and forth magnetising motor windings and charging power supplies without doing work. The ratio of real power (kW) to apparent power (kVA) is the power factor, and Fluke's power factor explainer walks through how it is measured on real circuits. The √3 (about 1.732) in the three-phase formula is geometry, not a fudge factor: the three phases sit 120 degrees apart, and line-to-line voltage is √3 times the line-to-neutral voltage, so the same power arrives with less current per conductor. After every conversion the tool prints the formula it actually used with your watts, volts and power factor substituted in, so you can audit the arithmetic line by line instead of trusting a bare number.
Worked examples for every current type and voltage
Each row below is a real run of the calculator above, including the pre-filled example in the first row. Enter any row exactly as written and the tool returns the figure in the last columns.
| Run | Input | Result | Apparent power |
|---|---|---|---|
| Three-phase, pre-filled example | 50 kW, 400 V, PF 0.8 | 90.21 A | 62.50 kVA |
| Three-phase, better power factor | 50 kW, 400 V, PF 0.9 | 80.19 A | 55.56 kVA |
| Single-phase, workshop load | 5 kW, 230 V, PF 0.8 | 27.17 A | 6.25 kVA |
| DC, battery bank | 5 kW, 100 V | 50.00 A | 5.00 kVA |
| Three-phase, North American industrial | 100 kW, 480 V, PF 0.9 | 133.65 A | 111.11 kVA |
| Three-phase, 208 V service | 10 kW, 208 V, PF 0.85 | 32.66 A | 11.76 kVA |
| Reverse, single-phase | 27.17 A, 230 V, PF 0.8 | 5.00 kW | 6.25 kVA |
Compare the first two rows and the power factor lesson lands: the same 50 kW at the same 400 V needs 90.21 A at PF 0.8 but only 80.19 A at PF 0.9. Nothing about the useful work changed; the lower power factor load simply drags about 12% more current through the same cables to do it.
Picking a power factor that does not wreck the answer
Use the nameplate or measured power factor when you have it, and an equipment preset when you do not. A guessed power factor is the single biggest error source in this calculation.
| Preset | Typical loads | Power factor |
|---|---|---|
| Resistive | Heaters, kettles, incandescent lamps, ovens | 1.0 |
| LED lighting | Modern LED drivers and lighting circuits | 0.9 |
| Motors | Induction motors near full load | 0.85 |
| HVAC | Compressors, air conditioning, refrigeration | 0.8 |
| Computers | Switch-mode power supplies, IT equipment | 0.7 |
Treat the presets as starting points, not specifications. A motor's power factor slides with its load: the same motor that sits near 0.85 at full load can drop far lower idling, which is one reason measured installations draw more current than a catalogue calculation promised.
From calculated amps to breakers and cable
The calculated current is the load's running current under ideal conditions, not a breaker size. The sizing figure in the result badge multiplies it by 125%.
Under NFPA 70, the National Electrical Code, continuous loads (running for three hours or more) are sized at 125% of their current for both the breaker and the conductor. That is why the pre-filled example's 90.21 A becomes a 112.76 A sizing figure: the next standard breaker at or above that, not a 90-amp device, is the starting point. The equipment nameplate still beats any calculation, because it already reflects the manufacturer's tested draw, and the conductor has to suit the breaker, the run length and the installation method. Once the current is settled, the electrical cable size calculator turns it into a conductor size. Anything beyond a like-for-like check belongs with a licensed electrician and the local code, a point the Occupational Safety and Health Administration's electrical safety pages make with considerably less humour than the average forum thread.
What this calculation leaves out
Four real-world factors sit outside these formulas, and pretending otherwise is how calculated installs fail inspection or trip on a hot afternoon.
- Efficiency: the formulas treat the kilowatts you enter as electrical input power. If your figure is a motor's shaft output, the electrical input is higher by the efficiency loss, and the current rises with it.
- Starting current: motors and compressors draw several times their running current for the first moments after switch-on. Breaker curves, not this steady-state sum, decide whether that inrush trips anything.
- Voltage drop: a long cable run loses voltage along its length, and a load at the far end of a sagging supply draws more current to do the same work. The formula assumes the nameplate voltage actually arrives.
- Unbalance and harmonics: the three-phase formula assumes a balanced load sharing current evenly across phases. Badly unbalanced panels and harmonic-heavy loads break that assumption in the direction of more heat, not less.
None of that makes the conversion useless; it makes it the first step rather than the last. And note what the answer is not: amps are not energy. The example load running for one hour uses 50 kWh (50 kW for one hour), and pricing that energy belongs to the cost per kWh calculator, not to a current conversion.
What competing calculators miss
Most pages in this SERP print the three equations and stop, and at least one widely read guide prints one of them wrong:
- EcoFlow's conversion guide: broad and readable, but its step-by-step list writes the three-phase denominator as (3 × V × PF) in one place, dropping the √3, and its single-phase walkthrough elsewhere omits the power factor it correctly includes in the formula box.
- CalculatorDock: clean formulas and a neat worked example, but one direction only, no power factor help, and no apparent power output, so generator and transformer checks need a second tool.
- Electrical-World's three-phase guide: deep on motors, including an efficiency-aware motor formula this page deliberately does not fold in, but it is a three-phase article; DC and single-phase readers are sent elsewhere.
- Generator Source: a full generator sizing suite (kVA, horsepower, sliders that update live) aimed at picking a generator, not at a quick circuit conversion; the breadth buries the simple question most visitors arrive with.
- KWCalculator: the strongest rival, with conversions to horsepower, kVA and BTU/hr and the formula substituted with your numbers, a feature this page matches. It spreads across many unit pairs, though; this page stays on the kW and amps pair and adds equipment power factor presets and the 125% sizing figure.
- CalculatorsConversion: adds an efficiency input for driven equipment, a genuine extra, but pairs it with long static reference tables rather than a formula readout for the reader's own numbers.
- The gap this page fills: both directions on one page, kVA beside every result, the formula printed with your numbers in it, power factor presets by equipment type, and the continuous-load sizing figure worked out instead of left as homework.
Frequently asked questions
It depends on the voltage and current type. At 230 V single-phase with 0.8 power factor, 1 kW draws about 5.43 A. At 400 V three-phase with 0.9 power factor, about 1.60 A. There is no single answer without voltage.
Power factor (0 to 1) is the ratio of real power to apparent power: how effectively a load turns current into useful work. Inductive loads like motors have lower power factors; resistive loads like heaters are 1.0.
Because the power is shared across three phases. The square root of 3 factor (about 1.732) in the denominator reflects the 120-degree phase relationships, so each conductor carries less current for the same total power.
The standard three-phase formula uses line-to-line voltage (for example, 400 V or 480 V). If you only know line-to-neutral, multiply it by the square root of 3 to get line-to-line first.
Use the result as a starting point, then apply the 125% continuous-load rule and check the equipment nameplate and local code. When in doubt, consult a licensed electrician.
kW is real power (does useful work); kVA is apparent power (what the supply must deliver). They differ by the power factor: kVA = kW / PF. Generators and transformers are rated in kVA.
Because DC has no phase shift for a power factor to describe. When you select DC, the calculator hides the field and forces the power factor to 1 internally. Anything left typed in the field is ignored, so a value above 1 that would be an error for AC converts normally for DC.
No. The formulas convert the electrical power you enter, at the power factor you enter, under steady running conditions. A motor's starting current can run several times its running current, and if the kilowatts you have are shaft output rather than electrical input, efficiency has to be accounted for before this conversion. Use the equipment nameplate for installed work.
Add This Calculator to Your Website
Embed this calculator on your own site with the code below. Pick a size to preview it live, then copy the code.
Powered by Calculator Zilo
References
- National Fire Protection Association. NFPA 70: National Electrical Code. Accessed October 22, 2026.
- Occupational Safety and Health Administration. Electrical Safety Standards and Hazards. Accessed October 22, 2026.
- Fluke Corporation. What Is Power Factor? Accessed October 22, 2026.
- All About Circuits, Textbook. True, Reactive, and Apparent Power. Accessed October 22, 2026.
- All About Circuits, Textbook. Power Factor (AC Circuits Textbook, Chapter 11). Accessed October 22, 2026.
- U.S. Department of Energy, Advanced Manufacturing Office. Improving Motor and Drive System Performance: A Sourcebook for Industry. Accessed October 22, 2026.