Watts, volts and amps are linked: doubling the current at the same voltage doubles the power.
How to use the Electrical Power Calculator
- Voltage
- Current
- Power factor
- Running time
- Want to work backwards? Type a value into Power and Current is calculated for you.
Results update as you type, and every field accepts the units shown in its menu.
How it works
Multiply voltage by current for DC or resistive AC loads. For other AC loads, multiply by the power factor.
Inputs explained
| Field | What to enter |
|---|---|
| Voltage | Units: V, mV, kV |
| Current | Units: A, mA, µA |
| Power factor | A number |
| Running time | Units: h, min, days |
What each result means
- Power = [Voltage] × [Current] × [Power factor]
- Resistance = [Voltage] ÷ [Current]
- Energy used = [Power] × [Running time] ÷ 1000
Example values
How the main result changes when Current changes and everything else stays at the example values above:
| Current (A) | Power (W) |
|---|---|
| 2.5 | 575 |
| 3.75 | 862.5 |
| 5 | 1,150 |
| 6.25 | 1,437.5 |
| 7.5 | 1,725 |
| 10 | 2,300 |
Formula
P = V × IR = V ÷ IEnergy = P × timeWorked example
Inputs — Voltage: 230 V; Current: 5 A; Power factor: 1; Running time: 2 h.
Results — Power = 1,150 W; Resistance = 46 Ω; Energy used = 2.3 kWh.
Frequently asked questions
What is power factor?
The ratio of real to apparent power in AC circuits; 1 for heaters and incandescent lamps.
How many amps does a 2 kW kettle draw at 230 V?
About 8.7 A.
What formula does the Electrical Power Calculator use?
P = V × I.
Can I work backwards from the result?
Yes. Type the result you want into Power and the calculator finds the matching current.