To convert watts to amps, divide the watts by the volts: amps = watts ÷ volts. A 1,500 W heater on 120 V draws 12.5 A, and the same heater on 230 V draws about 6.5 A. This free watts to amps calculator does the maths for DC, single-phase AC and three-phase AC, and it also converts amps to watts.
Watts to amps calculator
Find the current from the power and voltage, or the power from the current. Works for DC, single-phase AC and three-phase AC.
Watts to Amps Formulas
| Circuit | Watts to amps | Amps to watts |
|---|---|---|
| DC (batteries, cars, solar) | I = P ÷ V | P = V × I |
| AC single-phase (homes) | I = P ÷ (PF × V) | P = PF × V × I |
| AC three-phase | I = P ÷ (√3 × PF × V) | P = √3 × PF × V × I |
For three-phase, V is the voltage between two lines (line to line), such as 208 V, 400 V or 480 V. The power factor (PF) is 1 for heaters, kettles and incandescent bulbs, and usually 0.8 to 0.95 for motors and compressors.
Worked Examples
- A 60 W bulb on 120 V: 60 ÷ 120 = 0.5 A
- A 2,000 W kettle on 230 V: 2,000 ÷ 230 = 8.7 A
- A 120 W fridge on a 12 V battery: 120 ÷ 12 = 10 A
- A 5 kW three-phase motor on 400 V with a power factor of 0.85: 5,000 ÷ (1.732 × 0.85 × 400) = 8.5 A per line
If you also know resistance, the Ohm’s law calculator works out volts, amps, ohms and watts from any two values.
Watts to Amps Chart (120 V and 230 V)
Amps drawn by common loads at US (120 V) and UK, European and Asian (230 V) household voltage.
| Watts | Amps at 120 V | Amps at 230 V |
|---|---|---|
| 100 W | 0.83 A | 0.43 A |
| 200 W | 1.67 A | 0.87 A |
| 300 W | 2.5 A | 1.3 A |
| 500 W | 4.17 A | 2.17 A |
| 750 W | 6.25 A | 3.26 A |
| 1,000 W | 8.33 A | 4.35 A |
| 1,200 W | 10 A | 5.22 A |
| 1,500 W | 12.5 A | 6.52 A |
| 1,800 W | 15 A | 7.83 A |
| 2,000 W | 16.67 A | 8.7 A |
| 2,400 W | 20 A | 10.43 A |
| 3,000 W | 25 A | 13.04 A |
| 3,500 W | 29.17 A | 15.22 A |
| 5,000 W | 41.67 A | 21.74 A |
Watts to Amps at 12 V and 24 V DC
For car, RV, boat and solar systems. Low voltage means high current, so a small 12 V load can need thick wire.
| Watts | Amps at 12 V | Amps at 24 V |
|---|---|---|
| 10 W | 0.83 A | 0.42 A |
| 25 W | 2.08 A | 1.04 A |
| 50 W | 4.17 A | 2.08 A |
| 100 W | 8.33 A | 4.17 A |
| 150 W | 12.5 A | 6.25 A |
| 200 W | 16.67 A | 8.33 A |
| 300 W | 25 A | 12.5 A |
| 500 W | 41.67 A | 20.83 A |
| 1,000 W | 83.33 A | 41.67 A |
| 1,500 W | 125 A | 62.5 A |
| 2,000 W | 166.67 A | 83.33 A |
If you run a 230 V or 120 V appliance from a battery through an inverter, add about 10% for inverter losses. A 1,000 W load on a 12 V inverter pulls around 90 A or more from the battery.
Amps to Watts Chart (120 V and 230 V)
| Amps | Watts at 120 V | Watts at 230 V |
|---|---|---|
| 1 A | 120 W | 230 W |
| 2 A | 240 W | 460 W |
| 5 A | 600 W | 1,150 W |
| 10 A | 1,200 W | 2,300 W |
| 13 A | 1,560 W | 2,990 W |
| 15 A | 1,800 W | 3,450 W |
| 16 A | 1,920 W | 3,680 W |
| 20 A | 2,400 W | 4,600 W |
| 30 A | 3,600 W | 6,900 W |
How Many Watts Can a Circuit Handle?
Multiply the voltage by the breaker or fuse rating. For loads that run for 3 hours or more, such as heaters, stay under 80% of the rating.
| Circuit | Maximum | Continuous (80%) |
|---|---|---|
| 15 A at 120 V (US) | 1,800 W | 1,440 W (12 A) |
| 20 A at 120 V (US) | 2,400 W | 1,920 W (16 A) |
| 13 A plug at 230 V (UK) | 2,990 W | about 2,400 W |
| 16 A at 230 V | 3,680 W | about 2,940 W |
My guide to testing watts with a multimeter explains 15 A and 20 A outlets and how to work out a safe load in more detail.
Measure Real Watts and Amps With Your Meter
The wattage on a label is a rating, not what the device uses every second. To find the real numbers:
- Measure the supply voltage with your multimeter on AC or DC volts.
- Measure the current. For mains appliances, use a clamp meter around one wire. For small DC loads up to the meter’s limit (often 10 A), you can measure amps with a multimeter in series.
- Enter both numbers in the Amps to Watts mode above. For AC motors, the result is the apparent power unless you know the power factor.
Expect motors and compressors to show a big current spike for a second when they start. That is normal and is why their breakers are often larger than the running current suggests.
Frequently Asked Questions
How many amps is 1500 watts?
1,500 watts is 12.5 amps at 120 V and about 6.5 amps at 230 V. On a 12 V DC system the same 1,500 W would draw 125 amps.
How many amps is 2000 watts?
2,000 watts is about 16.7 amps at 120 V and about 8.7 amps at 230 V.
How many watts is 15 amps?
15 amps is 1,800 watts at 120 V and 3,450 watts at 230 V. For a continuous load on a 15 A circuit, stay under 80%, which is 12 A or 1,440 W at 120 V.
How many amps does 100 watts draw at 12 volts?
100 watts at 12 V DC draws about 8.3 amps (100 ÷ 12). At 24 V it is about 4.2 amps.
Can I convert watts to amps without the voltage?
No. The same power draws different current at different voltages, so you always need the voltage. Use the voltage printed on the device or measure it with a multimeter.
What is power factor?
Power factor shows how much of the current does useful work. Heaters, kettles and incandescent bulbs have a power factor of 1. Motors, compressors and many power supplies are lower, often 0.8 to 0.95, so they draw more amps than watts ÷ volts suggests.
Why does my clamp meter show more amps than the calculator?
Motors and compressors draw a large surge for a moment when they start, the power factor may be below 1, and the label is only a rating. Low supply voltage also raises the current for the same power.