# Power Dissipation Calculator

URL: https://speedycalculator.com/calculators/physics/power-dissipation/
Last updated: 2026-10-30

> The power dissipation calculator finds the power dissipated in each resistor of a series or parallel circuit connected to a voltage source, and the total power and current.

## Inputs

- Connection
- Source voltage (V, mV, kV, µV, MV)
- Resistor R1 (Ω, kΩ, MΩ, mΩ)
- Resistor R2 (Ω, kΩ, MΩ, mΩ)
- Resistor R3 (Ω, kΩ, MΩ, mΩ)
- Resistor R4 (Ω, kΩ, MΩ, mΩ)
- Resistor R5 (Ω, kΩ, MΩ, mΩ)
- Resistor R6 (Ω, kΩ, MΩ, mΩ)

## Results

- Equivalent resistance
- Total current
- Total power
- Power in R1
- Power in R2
- Power in R3
- Power in R4
- Power in R5
- Power in R6

## Formula

```
Series: I = V/ΣR,  P_i = I²·R_i · Parallel: P_i = V²/R_i
```

## Explanation

Every resistor turns electrical energy into heat. Knowing how much power each one dissipates tells you which resistor rating to choose and whether a circuit will overheat.

### How to use the Power Dissipation Calculator

- **Connection**
- **Source voltage**
- **Resistor R1**
- **Resistor R2**
- **Resistor R3**
- **Resistor R4**
- **Resistor R5**
- **Resistor R6**

Results update as you type, every field has its own unit menu, and everything is calculated in your browser.

### How it works

Choose series or parallel, enter the source voltage and up to six resistances (leave unused ones at 0).

### Inputs explained

FieldWhat to enterConnectionChoose one: Series, ParallelSource voltageUnits: V, mV, kV, µV, MVResistor R1Units: Ω, kΩ, MΩ, mΩResistor R2Units: Ω, kΩ, MΩ, mΩResistor R3Units: Ω, kΩ, MΩ, mΩResistor R4Units: Ω, kΩ, MΩ, mΩResistor R5Units: Ω, kΩ, MΩ, mΩResistor R6Units: Ω, kΩ, MΩ, mΩ

### Example values

How the main result changes when **Source voltage** changes and everything else stays at the example values above:

Source voltage (V)Total power (W)60.055490.1246120.2215150.3462180.4985240.8862

## Worked example

Inputs — Connection: Series; Source voltage: 12 V; Resistor R1: 100 Ω; Resistor R2: 220 Ω; Resistor R3: 330 Ω; Resistor R4: 0 Ω; Resistor R5: 0 Ω; Resistor R6: 0 Ω.

Results — Equivalent resistance = 650 Ω; Total current = 0.01846 A; **Total power = 0.22154 W**; Power in R1 = 0.03408 W; Power in R2 = 0.07498 W; Power in R3 = 0.11247 W; Power in R4 = 0 W; Power in R5 = 0 W; Power in R6 = 0 W.

## Key terms

- **Power rating**: Maximum safe dissipation of a component.

## FAQ

**In series, which resistor gets hottest?**
The largest one.

**In parallel, which resistor gets hottest?**
The smallest one.

**What rating should a resistor have?**
At least twice the dissipated power for reliability.

**Does total power depend on connection?**
Yes – parallel circuits draw much more from the same voltage.


## Sources

- [OpenStax – University Physics Volume 2](https://openstax.org/details/books/university-physics-volume-2)
- [The Engineering ToolBox](https://www.engineeringtoolbox.com/)