Practical tools for measured work
Watts, amps and volts calculator
Solve real power, voltage or current for DC, single-phase AC and balanced three-phase systems.
Calculate the layout, check the diagram, then print the result for the shop or jobsite.
How it works
DC power is VI. Single-phase AC real power is Vrms × Irms × power factor. Balanced three-phase real power is √3 × line-to-line RMS voltage × line current × power factor. Thus 120 W at 12 V DC draws 10 A. Power factor must be greater than zero and no more than one.
Current-input example
The result above uses these exact values. This snapshot is included when the page is printed so the output can be checked against the original measurements.
- Electrical system
- Direct current
- Solve for
- Line current
- Real power
- 120 W
- Voltage
- 12 V
Primary result: Real power: 120 W.
Before using the result
- Check the selected mode, units and input values before using the result.
- Read the assumptions and rounding rules; compare the worked example with your intended calculation.
- A numerical result does not supply missing context or change the stated limitations.
Limitations
The three-phase mode assumes a balanced load. AC voltage and current are RMS values. Motor output power requires an additional efficiency calculation before using electrical input power here. This relationship does not select a circuit breaker or conductor ampacity.
Frequently asked questions
What should I verify before using this result?
Check the input values, units, dates and assumptions. Compare the method and its stated limits with the source relevant to your task.
Why might the finished result differ?
Results depend on the entered data and the model’s assumptions. Rounding, changing conditions or omitted factors can affect the comparison. Read the limitations before using the result.
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