What this calculator does
Converting watts to amps needs a voltage in the mix: current is power divided by voltage, so the same wattage draws different current depending on what it is plugged into. A 2,200 W appliance draws roughly 9.6 A at 230 V mains, but closer to 18.3 A on a 120 V supply, which is why appliance ratings and circuit breakers are sized against a specific voltage.
The default voltage here is 230 V, common across most of the world’s mains supply, but it is a plain input you can change to 120 V, 400 V three-phase line voltage, or any DC voltage a project uses. A power factor field is included for AC loads such as motors that are not purely resistive, where the simple watts-over-volts figure understates the actual current drawn.
The formula
For watts to amps, current equals power divided by voltage, adjusted by the power factor: A = W ÷ (V × power factor). For amps to watts, the same relationship runs the other way: W = A × V × power factor. Power factor is 1 for DC circuits and for purely resistive AC loads such as heating elements and incandescent bulbs, and lower for reactive loads such as motors and some electronics.
| Term | Meaning |
|---|---|
| W | Power, in watts. |
| V | Voltage, in volts. |
| A | Current, in amps. |
| Power factor | The ratio of real power used to apparent power drawn, between 0 and 1. Purely resistive loads sit at 1. |
The inputs explained
| Field | What to enter |
|---|---|
| Convert | Choose whether you are converting a known wattage into amps, or a known current into watts. |
| Power (W) | The power rating, used when converting watts to amps. |
| Voltage (V) | The supply voltage. 230 V and 120 V cover most household mains; use the actual supply voltage for anything else. |
| Current (A) | The current rating, used when converting amps to watts. |
| Power factor (1 for DC or purely resistive AC loads) | Leave at 1 for DC or resistive AC loads. Use the equipment’s stated power factor for motors and other reactive loads. |
When to use it
Sizing a circuit breaker or cable for an appliance
Converting an appliance’s wattage to amps at the supply voltage tells you the current a circuit needs to carry, which is what a breaker rating and cable size are chosen against, not the wattage itself.
Checking a nameplate current rating
Many appliances list both a wattage and an amp rating; running the wattage through this calculator at the stated voltage is a quick check that the two figures are consistent.
Comparing 120 V and 230 V appliances
The same load draws roughly twice the current at 120 V that it does at 230 V, which is why cabling and plug standards differ so much between regions running different mains voltages.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How many amps common appliance wattages draw at 230 V
A range of typical appliance wattages, converted to current at 230 V.
| Power | Current | In milliamps |
|---|---|---|
| 100 W | 0.43 A | 435 mA |
| 500 W | 2.17 A | 2,174 mA |
| 1000 W | 4.35 A | 4,348 mA |
| 1500 W | 6.52 A | 6,522 mA |
| 2000 W | 8.70 A | 8,696 mA |
| 3000 W | 13.04 A | 13,043 mA |
How the current needed for a fixed load changes with supply voltage
A fixed 2,200 W load, run at a range of supply voltages.
Questions
Why do I need a voltage to convert watts to amps?
Watts measure total power, which is current multiplied by voltage. The same power can be delivered as a lot of current at a low voltage or a little current at a high voltage, so watts alone do not fix the amps: a voltage has to be specified.
What voltage should I use for a household appliance?
Use the supply voltage the appliance is actually plugged into: commonly 230 V or 240 V across most of the world, and 120 V in North America and parts of Japan. Check a local outlet or the appliance’s own rating plate if unsure.
What is power factor and when does it matter?
Power factor is the ratio of the power actually doing useful work to the total apparent power drawn from the supply. It matters for AC loads with motors, ballasts or switching electronics, where it is often noticeably below 1; leave it at 1 for DC circuits and purely resistive loads like heaters.
Is this the same as Ohm’s law?
They are related but not identical: Ohm’s law relates voltage, current and resistance directly, while this calculator relates power, voltage and current, with power factor standing in for the effect resistance and reactance together have on an AC load. For the resistance-based version, see the Ohm’s law calculator.
For the full relationship between voltage, current, resistance and power, see the Ohm’s law calculator. To work out what a given load costs to run over time, use the electricity running cost calculator.