# Electrical Power Calculator (Watts, Volts, Amps)

URL: https://speedycalculator.com/calculators/physics/electrical-power/
Last updated: 2026-10-25

> The electrical power calculator finds power from voltage and current, P = V × I, and also gives the resistance and energy used over time. Type a power to solve for current.

## Inputs

- Voltage (V, mV, kV)
- Current (A, mA, µA)
- Power factor
- Running time (h, min, days)

## Results

- Power
- Resistance
- Energy used

## Formula

```
P = V × I
R = V ÷ I
Energy = P × time
```

## Explanation

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

FieldWhat to enterVoltageUnits: V, mV, kVCurrentUnits: A, mA, µAPower factorA numberRunning timeUnits: 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)2.55753.75862.551,1506.251,437.57.51,725102,300

## Worked 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.

## FAQ

**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.


## Sources

- [NIST – Fundamental physical constants](https://physics.nist.gov/cuu/Constants/)