Resistor Power Dissipation
Enter any two
Fill exactly two of V, I, R to find the dissipated power and a recommended rating.
Dissipated power & rating
How to use this calculator
A resistor converts electrical power into heat, and if it dissipates more than its rating it overheats and fails. This tool takes any two of voltage V, current I and resistance R, computes the dissipated power P = V·I = I²·R = V²/R, and recommends the smallest standard power rating (⅛ W up to 50 W) that is at least as large as P times the design margin you choose. It also shows the third electrical quantity for completeness.
What it means in a real circuit
Checking dissipation is one of the most common reliability steps in design. A resistor that only "just" fits its power rating runs hot, drifts in value and ages quickly — so a design margin (often 2× for continuous loads) is good practice. The tool makes that check explicit: enter what you know about the resistor in the circuit, see the watts it must handle, and pick a rating with headroom. That's the difference between a resistor that lasts a decade and one that smokes on power-up.