Electrical
Watts to Amps Calculator
Compare the current implied by a power requirement across DC, single-phase and balanced three-phase supply assumptions.
Result
A planning estimate, not a code calculation. Conductor sizing, overcurrent protection and load calculations are governed by the NEC as adopted and amended where you are, and by the listing of the equipment involved. Have the design confirmed by a licensed electrician and inspected.
Get a Free Business AuditWhat moves the number
- Electrical input watts differ from advertised mechanical output.
- A lower AC power factor increases the current needed for a given real power.
- The selected voltage and system must describe the same equipment connection.
Where this one goes wrong
The smallest-breaker output is only a lookup beside the current conversion. It does not establish whether a device will ride through starting current, protect the selected cable or meet equipment-specific instructions.
Questions
About this calculator
Can I compare two supply voltages here?
Yes, as an arithmetic scenario using the same power and compatible system assumptions. That comparison does not prove the appliance can be reconnected to either voltage.
What does the continuous-load figure represent?
It shows the additional planning allowance built into this tool. It is not an estimate of extra energy consumed while equipment runs longer.
What must be checked before installation?
Current conversion is a planning aid. The adopted electrical code, actual conductor conditions and equipment listing govern the final circuit and overcurrent protection.
The formula
single phase: A = W / (V x PF); three phase: A = W / (1.732 x V x PF)
Put this calculator on your site
Free to embed. Paste this where you want it to appear. It stays up to date automatically because it loads from BDEVY.
Please keep the attribution line. It is the only thing we ask in return.
How to use this calculator
- Power (watts). Enter your own figure; the page starts at 1,800.
- 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 current, 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 |
|---|---|
| Power (watts) | 1,800 |
| Voltage | 120 |
| System | AC single phase |
| Power factor | 1 |
What comes out
| Result | Value |
|---|---|
| Current main result | 15.0 |
| Smallest standard breaker | 15 |
| If the load is continuous | 20 |
| Power | 1.8 |
15.0 amps, which wants a 15 amp breaker, or 20 if the load runs for three hours or more.
How sensitive the answer is
Holding everything else steady and changing only power (watts), this is what happens to current. It is worth knowing which of your inputs the answer actually hinges on, and which barely move it.
| Power (watts) | Current |
|---|---|
| 900 | 7.5 |
| 1,350 | 11.3 |
| 1,800 example above | 15.0 |
| 2,700 | 22.5 |
| 3,600 | 30.0 |
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
- Power (watts)
- A number, between 0 and 5000000, starting at 1,800.
- 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 |
|---|---|
| Current | The headline result. A decimal figure. |
| Smallest standard breaker | A number. |
| If the load is continuous | A number. |
| Power | 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
Related calculators
Amps to Watts Calculator
Translate a stated input current into DC or AC power while keeping electrical input separate from mechanical output.
Open calculatorElectrical Breaker Size Calculator
Explore a preliminary breaker lookup from an entered current or a simple watts-to-current conversion.
Open calculatorEstimating is the easy part
The jobs you never hear about cost more than the ones you mis-measure. BDEVY builds the marketing, systems and automation that bring them in.