Amps to Watts Calculator
Convert amperes to watts using voltage. Watts measure electrical power, while amps measure current. The conversion depends on voltage and circuit type (DC or AC). Use this calculator for electrical load planning, circuit sizing, and appliance power estimation.
How to Convert Amps to Watts
The relationship between amps and watts is defined by the power equation. For DC circuits and simple AC circuits:
DC: P(W) = I(A) × V(V)
AC Single-Phase: P(W) = I(A) × V(V) × PF
AC Three-Phase: P(W) = √3 × I(A) × V(V) × PF
Where P is power in watts, I is current in amperes, V is voltage in volts, and PF is the power factor (typically 0.8 for inductive loads like motors).
Example Calculation
A 15-amp circuit at 120 volts (standard US household outlet): P = 15A × 120V = 1,800 watts. This means the circuit can handle up to 1,800 watts of electrical load — enough for a space heater or hair dryer.
Amps to Watts Reference Table (DC)
| Amps | Voltage | Watts |
|---|---|---|
| 1 A | 120 V | 120 W |
| 5 A | 120 V | 600 W |
| 10 A | 120 V | 1,200 W |
| 15 A | 120 V | 1,800 W |
| 20 A | 120 V | 2,400 W |
| 5 A | 220 V | 1,100 W |
| 10 A | 220 V | 2,200 W |
| 15 A | 220 V | 3,300 W |
| 20 A | 220 V | 4,400 W |
| 30 A | 240 V | 7,200 W |
| 50 A | 240 V | 12,000 W |
| 100 A | 240 V | 24,000 W |
Frequently Asked Questions
How many watts is 1 amp at 120 volts?
1 amp at 120 volts equals 120 watts in a DC circuit. For AC circuits, multiply by the power factor (typically 0.8), giving approximately 96 watts.
How many watts is 15 amps?
15 amps at 120V = 1,800 watts. At 240V = 3,600 watts. The wattage depends on the voltage of your circuit.
What is the difference between amps and watts?
Amps measure the flow of electrical current (how many electrons pass a point per second). Watts measure power (the rate at which energy is consumed). You need both amps and voltage to calculate watts.
How many amps is 1000 watts at 120V?
1000 watts ÷ 120 volts = 8.33 amps. This is the current draw of a typical 1000W appliance on a standard US outlet.
What is power factor?
Power factor is the ratio of real power to apparent power in an AC circuit. It ranges from 0 to 1. Resistive loads (heaters, incandescent bulbs) have a PF of 1.0. Inductive loads (motors, transformers) typically have a PF of 0.7-0.9.
Amps to Watts vs Amps to Kilowatts
Watts and kilowatts measure the same thing — electrical power — just at different scales. 1 kilowatt = 1,000 watts. For household appliances (hair dryers, microwaves, space heaters), watts are more practical. For larger loads (HVAC systems, electric vehicle chargers, industrial motors), kilowatts are standard. To convert amps to kilowatts, simply divide the watt result by 1,000.
Practical Applications
- Circuit breaker sizing: A 20A breaker at 120V handles up to 2,400W (use 80% rule: 1,920W continuous)
- Generator sizing: Add up all appliance wattages to determine minimum generator capacity
- Extension cord rating: Match cord amperage rating to the total watts of connected devices
- Solar panel systems: Calculate how many amps your panels produce at system voltage to determine wattage output
- EV charging: A 50A, 240V Level 2 charger delivers 12,000W (12 kW) to your vehicle
- Electrical safety: Never exceed 80% of a circuit's rated amperage for continuous loads (NEC Article 210.20)
Understanding Power Factor in AC Circuits
In AC circuits, the power factor (PF) represents the efficiency of power delivery. A PF of 1.0 means all current is doing useful work (purely resistive loads like heaters). A PF of 0.8 means only 80% of the apparent power is real power — the rest is reactive power that oscillates between source and load without doing work. Motors, transformers, and fluorescent lighting typically have power factors between 0.7 and 0.9. Power factor correction capacitors can improve PF closer to 1.0, reducing current draw and electricity costs.