Electrical
Amps to Watts Calculator
Translate a stated input current into DC or AC power while keeping electrical input separate from mechanical output.
Result
Power factor only applies to AC. Resistive loads such as heaters and incandescent lamps sit at 1; motors and electronics sit lower, which is why a motor draws more current than its wattage alone suggests.
Get a Free Business AuditWhat moves the number
- Select DC, single-phase AC or balanced three-phase AC deliberately.
- Voltage and current must describe the same supply condition.
- Power factor affects AC real power but is not a motor-efficiency input.
Where this one goes wrong
The horsepower equivalent is just a unit conversion from calculated input watts. It is not the usable shaft output of a motor and should not be compared directly with a mechanical nameplate rating to judge efficiency.
Questions
About this calculator
Why does power factor not change the DC result?
The DC calculation uses voltage times current. The AC phase relationship represented by power factor does not apply to that mode.
Does a breaker marked with amps tell me consumed watts?
Its rating is not a measurement of the operating load. Use equipment input data or an appropriate measured current rather than assuming full breaker current is always drawn.
Can the result size a supply?
It is an initial planning comparison. Capacity and protection still require code and manufacturer checks, including behavior that the steady-state conversion does not model.
The formula
single phase: W = V x A x PF; three phase: W = 1.732 x V x A x PF; DC: W = V x A
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How to use this calculator
- Current (amps). Enter your own figure; the page starts at 15.
- Voltage. Enter your own figure; the page starts at 120.
- System. Enter your own figure; the page starts at AC single phase.
- Power factor. Enter your own figure; the page starts at 1.
The result updates as you type, so you can try a figure, see what it does to power, and change it back. Nothing you enter is sent anywhere or saved.
A worked example
These are the figures the calculator opens with. Every number in the results column below is produced by the same calculation the page runs, so you can follow it through before putting your own figures in.
What goes in
| Input | Value |
|---|---|
| Current (amps) | 15 |
| Voltage | 120 |
| System | AC single phase |
| Power factor | 1 |
What comes out
| Result | Value |
|---|---|
| Power main result | 1,800 |
| In kilowatts | 1.8 |
| Apparent power | 1,800 |
| In horsepower | 2.4 |
1,800 watts (1.8 kW).
How sensitive the answer is
Holding everything else steady and changing only current (amps), this is what happens to power. It is worth knowing which of your inputs the answer actually hinges on, and which barely move it.
| Current (amps) | Power |
|---|---|
| 7.5 | 900 |
| 11.25 | 1,350 |
| 15 example above | 1,800 |
| 22.5 | 2,700 |
| 30 | 3,600 |
Every other input is held at the example value while this one changes, which is not how a real job behaves. Treat it as a guide to which number matters most, not as five separate quotes.
What each figure means
- Current (amps)
- A number, between 0 and 5000, starting at 15.
- Voltage
- A number, between 0 and 50000, starting at 120.
- System
- Choose from DC, AC single phase, AC three phase.
- Power factor
- A number, between 0.1 and 1, starting at 1.
What the results tell you
| Result | What it is |
|---|---|
| Power | The headline result. A number. |
| In kilowatts | A decimal figure. |
| Apparent power | A number. |
| In horsepower | A decimal figure. |
Before you rely on this number
Conductor sizing, voltage drop and load figures are governed by code, and the code takes precedence over any calculator. Ambient temperature, conduit fill, continuous load factors and the specific installation all change the answer. Treat this as a first pass, not a design.
Keep going
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