Calculating your power dissipated is straightforward once you know the Resistor Power formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Resistor Power Calculator.
What is Resistor Power?
The Resistor Power calculation tells you your power dissipated from a few simple inputs. The figure you are solving for here is the power dissipated.
The Resistor Power formula
The core formula is:
Power dissipated = Voltage across resistor ^ 2 ÷ ResistanceHere is what each input means:
- Voltage across resistor — a value measured in V. Example: 12 V.
- Resistance — a value measured in Ω. Example: 100 Ω.
How to calculate it step by step
- Write down the voltage across resistor (for example, 12 V).
- Write down the resistance (for example, 100 Ω).
- Apply the formula above to get your power dissipated.
- Double-check the result with the Resistor Power Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Voltage across resistor | 12 V |
| Resistance | 100 Ω |
| Power dissipated | 1.4400 |
| Current | 0.1200 |
With voltage across resistor of 12 V and resistance of 100 Ω, the power dissipated works out to 1.4400.
Example 2
With voltage across resistor of 24 V and resistance of 100 Ω, the power dissipated works out to 5.7600.
| Result | Value |
|---|---|
| Power dissipated | 5.7600 |
| Current | 0.2400 |
Example 3
With voltage across resistor of 6 V and resistance of 100 Ω, the power dissipated works out to 0.3600.
| Result | Value |
|---|---|
| Power dissipated | 0.3600 |
| Current | 0.0600 |
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
Prefer not to do the maths by hand? — the Resistor Power Calculator does it instantly, for free, with the formula and a worked example built in.
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