Calculation reviewed: 4 October 2026 · Engineering Desk Tools
How to use the Amps to kW calculator
Convert AC line current into electrical input power using voltage and power factor. Start with measurements or documented values for the equipment and reporting period you actually want to assess. The calculator does not fill in a typical installation for you. Its blank fields help keep a demonstration value from being mistaken for your own operating data.
Choose the required options, enter the values in the labelled units and select Calculate. If a field is rejected, check its range and unit before changing it. The result is accompanied by the equation and assumptions so you can decide whether it answers your engineering question.
Inputs and measurement basis
- Supply. Use three-phase for a balanced three-phase supply and single-phase for a two-wire circuit.
- Line current (A). Measured line current in amps. For balanced three-phase use the average of the three lines.
- Supply voltage (V). Supply voltage; line-to-line for three-phase. The value must be greater than zero.
- Power factor (decimal, up to 1). Power factor as a decimal such as 0.85, not 85. The allowed maximum is 1. The value must be greater than zero.
Record the measurement source and operating condition. Retain unrounded values for verification.
Method and interpretation
The three-phase expression assumes balanced loading and a suitable measured power factor. A simple clamp-meter current reading alone cannot reveal active power. Where harmonic distortion or imbalance is important, a suitable power analyzer is preferable to substituting a guessed power factor. The result describes electrical input, not useful mechanical output.
Single-phase: kW = V × I × PF / 1000. Three-phase: kW = √3 × V × I × PF / 1000.
Use RMS voltage and current measured over the same operating condition, with power factor greater than 0 and up to 1. For balanced three-phase supplies, enter line-to-line voltage. The result is electrical input power; motor shaft output also depends on efficiency.
Worked example
This example does not populate the form. Enter your own installation data.
Calculated result: 15.2745 kW. Estimated active electrical input power
Check the arithmetic independently using the displayed equation. Retain intermediate precision and compare the final value with your equipment documentation.
Quick-reference table
These illustrative rows retain the worked example assumptions except for the varied input. They are not certified ratings or manufacturer data. Use the form for intermediate values.
Common mistakes
Adding three line currents before entering the current; assuming a power factor of one without evidence; interpreting electrical input as shaft output. Before relying on the output, check the decimal format, unit scale and source of each value. Recheck unusual results against the formula.
Frequently asked questions
Are the example values used automatically?
No. Inputs remain blank when the tool opens or when you clear them. The worked example and table are reading material below the calculator. Enter the actual values you want to check each time, and label saved reports so their context is not lost.
What does the result mean?
The result is the estimated active electrical input power for the measured current, voltage and power factor. It is not the shaft output of a motor: efficiency separates the two.
Can I use a zero or a negative value?
The allowed range follows the meaning of each input. A divisor needs a positive value; other fields may allow zero. Check the form labels and error message rather than forcing an invalid value. A rejected input must be corrected before a result can be shown.
Is this a final design or equipment approval?
No. Use RMS voltage and current measured over the same operating condition, with power factor greater than 0 and up to 1. For balanced three-phase supplies, enter line-to-line voltage. The result is electrical input power; motor shaft output also depends on efficiency. Use the calculation as support for a checked decision, and review equipment documentation and applicable requirements before changing an installation or operating setting.
How can I save or share a calculation?
Calculate first, then use Copy result or Print report. Some maintenance tools also provide a CSV summary. Reports contain your own entered data, so review them before sharing. You can share the public page URL without including plant records or confidential measurements.
How do I report an unexpected result?
Use the Contact page and include the tool URL, input values, units, expected output and the reference you used. Explain the measurement basis. Exclude confidential information.
Related tools and records
Use related calculations with consistent units, periods and equipment scope.
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