Watts to Amps Calculator
Need to know the current a device draws? This calculator converts watts to amps using your voltage and, for AC, the power factor.
Quick answerAt 230 V single-phase and power factor 1, divide watts by 230: 5 W is 0.022 A, 100 W is 0.43 A, 1,000 W is 4.35 A, and 2,000 W is 8.70 A. At 120 V, 1,000 W is 8.33 A. Balanced three-phase current also uses the √3 factor.
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How it works
DC or single-phase amps = watts ÷ (volts × power factor). Balanced three-phase amps = watts ÷ (√3 × line-to-line volts × power factor). For DC or purely resistive loads the power factor is 1.
Watts to amps chart at common voltages
The 120 V and 230 V columns are DC or single-phase at power factor 1. The last column is balanced three-phase at 400 V line-to-line and power factor 0.8.
| Power | 120 V, 1-phase | 230 V, 1-phase | 400 V, 3-phase, PF 0.8 |
|---|---|---|---|
| 100 W | 0.83 A | 0.43 A | 0.18 A |
| 500 W | 4.17 A | 2.17 A | 0.90 A |
| 1,000 W | 8.33 A | 4.35 A | 1.80 A |
| 1,500 W | 12.50 A | 6.52 A | 2.71 A |
| 2,000 W | 16.67 A | 8.70 A | 3.61 A |
Calculated current is not a substitute for the nameplate, manufacturer instructions, electrical code, or qualified circuit design.
Worked example: 1,200 W at 120 V and 0.8 power factor
Divide 1,200 W by 120 V × 0.8. The result is 12.5 A.
If the same 1,200 W load had power factor 1, the result would be 10 A. The lower power factor requires more current to deliver the same real power, which is why copying a generic “watts ÷ volts” answer can understate AC current.
How the three-phase option uses voltage
For DC or single-phase, select the first option. For balanced three-phase, select the second option and enter line-to-line voltage—not line-to-neutral voltage. The calculator uses √3 × line-to-line volts × line current × power factor.
Schneider Electric’s meter-verification documentation expresses the same balanced three-phase relationship as three times the line-to-neutral contribution. The √3 form is equivalent when line-to-line voltage is used.
Why calculated amps can differ from a label or meter
A device may change current as heaters cycle, motors start, compressors ramp, or electronic power supplies change load. Nameplates can show rated or maximum input rather than the momentary value. Voltage also varies around its nominal figure.
Use this conversion to understand a known real-power figure, not to size conductors, breakers, inverters, or generators. Those decisions can depend on continuous-load rules, startup current, duty cycle, temperature, wiring method, and the manufacturer’s specified circuit requirements.
Sources used for assumptions: Schneider Electric — single-phase and balanced three-phase power calculations; U.S. Energy Information Administration — electricity glossary; Klein Tools — CL390 true-RMS clamp meter specifications.
Frequently asked questions
What voltage should I use?
Use your local mains voltage — about 120 V in North America and 230 V in Europe and the UK. For car or battery circuits, use the DC voltage (often 12 V).
What is power factor?
It describes how effectively current is converted to useful power in AC circuits. Resistive loads are 1.0; motors and some electronics are lower (e.g. 0.8).
How many amps is 1,000 watts?
At 120 V and power factor 1, 1,000 W is about 8.33 A. At 230 V it is about 4.35 A. At 120 V and power factor 0.8 it is about 10.42 A.
Does this work for three-phase power?
Yes, for a balanced three-phase load. Select the three-phase option, enter line-to-line voltage and the per-line power factor, and the calculator applies the √3 relationship. Use manufacturer data for unbalanced or unusual systems.
Can I size a breaker or wire from this result?
No. Use the equipment nameplate and manufacturer instructions, and follow applicable electrical code with qualified guidance. Startup and continuous-load requirements are not captured by this simple conversion.
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