Watts to Amps Converter
| Appliance | Watts | Amps at 120 V | Amps at 240 V |
|---|---|---|---|
| phone charger | 10 | 0.08 | 0.04 |
| incandescent bulb | 60 | 0.50 | 0.25 |
| lamp / old TV | 100 | 0.83 | 0.42 |
| small microwave | 600 | 5.00 | 2.50 |
| space heater / kettle | 1,500 | 12.50 | 6.25 |
| dryer / EV charger | 5,000 | 41.67 | 20.83 |
One division runs the whole show: amps = watts / volts. The number every US household meets: a 1,500-watt space heater on a 120-volt circuit draws 12.5 amps - five-sixths of a 15-amp breaker, which is why the heater and the microwave argue about whose turn it is. The converter also does the two cases a bare formula hides: three-phase systems (divide by 1.732 extra with line-to-line voltage) and power factor (a 0.9-PF motor pulls 11% more current for the same watts).
This page is for the moment before you plug in or buy: sizing a generator against a tool's plate, checking whether an EV charger or dryer fits a circuit, seeing why a 5,000-watt appliance needs 240 volts - at 120 V it would demand 41.7 amps, more than any household circuit allows. The table below lists the appliances people actually convert, from phone chargers to water heaters, with their amps at both household voltages.
How to use
- Type the watts from the appliance plate or spec sheet (kW welcome - flip the unit), and amps appear instantly.
- Match the voltage to the circuit: 120 V for US outlets, 240 V for dryers, ranges and EV chargers, or pick three-phase for shop equipment.
- Leave power factor at 1.00 for heaters and incandescent loads; drop to 0.90 or 0.80 for motors, compressors and pumps.
Frequently asked questions
How many amps is 1500 watts?
12.5 amps at 120 V, or 6.25 amps at 240 V - the same watts, half the current, because volts and amps trade against each other for fixed power. That 12.5 A figure is why a 1,500-watt heater is the practical maximum for a 15-amp circuit: adding almost anything else trips the breaker, and continuous loads should really sit at 80% of the rating anyway.
What is the formula for watts to amps?
Amps = watts / volts for single-phase and DC. Three-phase adds a factor: amps = watts / (1.732 x volts-line-to-line x power factor). Power factor is the honest third variable: watts measure real work, but the current also carries magnetizing current for motors, so a 0.8-PF motor draws 25% more amps than watts alone suggests.
Why do 240-volt appliances need fewer amps?
They do not - they need half as many. Power is the product of volts times amps, so moving from 120 V to 240 V halves the current for the same watts: a 5,000-watt dryer draws 41.7 A at 120 V (impossible on household wiring) but a comfortable 20.8 A at 240 V. Thinner copper, cooler wires, same heat delivered.
Does power factor matter for heaters?
No - heaters, kettles and incandescent bulbs are resistive: current and voltage peak together and the power factor is effectively 1.00. It matters for anything with a motor, compressor or switch-mode supply: refrigerators, air conditioners, power tools. For those, the plate usually lists FLA (full-load amps) already - trust the plate over a watts conversion when wiring.
How do I convert kilowatts to amps?
Multiply kW by 1,000 first, then divide - 7.2 kW at 240 V is 30 amps, the classic hardwired EV-charger circuit. Three-phase shops do the same with the 1.732 factor: a 10 kW machine on 208 V three-phase at 0.9 PF draws about 30.8 amps per leg. The unit switch above handles the x1,000 so the math stays one step.