Watts to Amps Calculator
Convert watts (power) to amps (current) using voltage. This calculator supports DC circuits, single-phase AC, and three-phase AC power systems. The basic formula is Amps = Watts / Volts for DC circuits.
How to Convert Watts to Amps
- Determine the power in watts and the voltage of the circuit.
- For DC: divide watts by volts to get amps.
- For single-phase AC: divide watts by (volts x power factor).
- For three-phase AC: divide watts by (sqrt(3) x volts x power factor).
Formula
DC: Amps = Watts / Volts
AC (single-phase): Amps = Watts / (Volts x PF)
AC (three-phase): Amps = Watts / (sqrt(3) x Volts x PF)
Example Calculation
A 1500W heater on a 120V DC circuit:
Amps = 1500W / 120V = 12.5A
A 1500W motor on 120V AC with PF 0.85:
Amps = 1500 / (120 x 0.85) = 1500 / 102 = 14.71A
Watts to Amps Reference Table (DC)
| Power | Voltage | Current |
|---|---|---|
| 100W | 120V | 0.83A |
| 500W | 120V | 4.17A |
| 1000W | 120V | 8.33A |
| 1500W | 120V | 12.50A |
| 2000W | 120V | 16.67A |
| 1000W | 240V | 4.17A |
| 2000W | 240V | 8.33A |
| 3000W | 240V | 12.50A |
| 5000W | 240V | 20.83A |
Frequently Asked Questions
What is a power factor?
Power factor is the ratio of real power to apparent power in an AC circuit. It ranges from 0 to 1, with 1 being ideal (purely resistive load). Motors and inductive loads typically have a power factor of 0.7-0.9.
How many amps does a 1500 watt heater draw?
On a 120V circuit: 1500/120 = 12.5 amps. On a 240V circuit: 1500/240 = 6.25 amps.
Why does AC require power factor in the calculation?
In AC circuits, voltage and current may not be in phase. The power factor accounts for this phase difference. Only the in-phase component does useful work (real power).
What is the difference between single-phase and three-phase?
Single-phase uses one AC waveform (residential). Three-phase uses three waveforms 120 degrees apart (industrial/commercial), delivering more power with less conductor material.
How do I know what voltage my circuit uses?
In the US, standard outlets are 120V and large appliance outlets are 240V. In Europe and most other countries, standard voltage is 220-240V.