Physics

Resistor Wattage Calculator

Find the power a resistor dissipates and a safe rating.

Calculated Output

Power dissipated (W) 2.2

Recommended rating (2×) (W) 4.4

Formula: P = I²·R

Step-by-Step Breakdown

1. Values used:

2. Current = 0.1 A

3. Resistance = 220 Ω

5. Power dissipated = 2.2W

6. Recommended rating (2×) = 4.4W

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The math behind it

P = I²·R. Choose a resistor rated at least twice this for safety margin.

0.1 A through 220 Ω → 2.2 W (use a 4.4 W+ rating).

Why double the rating?

Running near the limit overheats parts; a 2× margin improves reliability.