Compared to other calculators we have posted, this one is extremely simple. Even if the formula for DC heat dissipation in a resistor isn't at your fingertips, a little Ohm's Law and the definition of power can easily create it. On the other hand, forgetting to calculate power ratings, particularly for cathode resistors and RC ripple filters, is one of the most common mistakes designers make. Ditto for placing a heat-sensitive capacitor next to some amp-warming ohms. So hopefully the mere presence of this calculator will serve as a reminder to include heat dissipation concerns in the final design. The calculator computes the DC heat dissipation in a resistor based on its value and either the voltage across it or the current through it.