Ohm Calculator
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Amps equal watts divided by volts, so any wattage rating can be turned into a current draw once you know the circuit voltage — the steps, charts, and appliance examples below show exactly how.
How to Calculate Watts to Amps
Amps measure the current flowing through a circuit, while watts measure power. To find the current an appliance draws, rearrange the power equation (P = I × V) and divide the power in watts by the circuit voltage. In symbols, I = P ÷ V.
- Read the power (P) in watts — from the appliance's rating plate or spec sheet.
- Identify the voltage (V) — 120 V for standard US outlets, 230–240 V for large appliances and most of Europe, or 12 V for automotive and solar systems.
- Divide watts by volts — the result is the current in amps. Example: 1,500 W ÷ 120 V = 12.5 A.
Need to go the other way? If you know the current and want the power, use our Amps to Watts calculator.
Watts to Amps Conversion Charts
The same wattage draws a very different current depending on the supply voltage — the higher the voltage, the lower the current for the same power. These charts convert common wattages to amps at three everyday voltages.
| Watts | Amps |
|---|---|
| 100 W | 0.83 A |
| 500 W | 4.17 A |
| 1,000 W | 8.33 A |
| 1,500 W | 12.5 A |
| 2,000 W | 16.67 A |
| Watts | Amps |
|---|---|
| 100 W | 0.42 A |
| 500 W | 2.08 A |
| 1,000 W | 4.17 A |
| 1,500 W | 6.25 A |
| 2,000 W | 8.33 A |
| Watts | Amps |
|---|---|
| 100 W | 8.33 A |
| 500 W | 41.67 A |
| 1,000 W | 83.33 A |
| 1,500 W | 125 A |
| 2,000 W | 166.67 A |
Common Appliance Conversions
How many amps does a 1500 watt heater use?
On a 120 V US circuit, a 1,500-watt heater draws 1,500 ÷ 120 = 12.5 amps. That is why space heaters are usually given their own outlet — at 12.5 A a single heater already uses most of a 15-amp circuit's safe continuous capacity (1,440 W). On a 240 V supply the same heater would draw just 6.25 A.
How many amps is a 1200 watt microwave?
A 1,200-watt microwave on a 120 V circuit pulls 1,200 ÷ 120 = 10 amps. Keep in mind that the advertised "1,200 watts" is often the cooking power — the power actually drawn from the outlet can be higher, which is why microwaves are commonly placed on a dedicated 20-amp circuit.
Frequently Asked Questions
What is Ohm's Law? +
Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points, expressed as V = I × R (Voltage = Current × Resistance). It's the foundation for calculating power, where Watts = Amps × Volts.
How do I convert watts to kilowatts? +
Divide the number of watts by 1,000. For example, 2,500 watts equals 2.5 kilowatts. Kilowatts are typically used to describe larger loads and to measure energy consumption on your utility bill.
How is my electricity bill calculated? +
Utilities charge per kilowatt-hour (kWh). Multiply an appliance's power in kilowatts by the hours it runs to get kWh consumed, then multiply by your electricity rate. The Energy Cost tab above does this automatically for daily, monthly, and yearly estimates.
What is a kilowatt-hour (kWh)? +
A kilowatt-hour is a unit of energy equal to running a 1,000-watt appliance for one hour. It is the standard unit used by energy providers to measure and bill electricity usage.