How is the Q of an RLC parallel resonant circuit calculated?

The Quality factor (Q) of a parallel RLC circuit is a measure of its energy storage relative to its energy loss. For a parallel resonant circuit, Q is calculated as the parallel resistance divided by the reactance of either the inductor or the capacitor (since their reactances are equal at resonance). Mathematically, this is Q = R / X. Note that this is the exact inverse of a series RLC circuit, where Q is calculated as the reactance divided by the resistance (Q = X / R). Remembering this distinction is crucial because test makers frequently offer the series formula as a distractor.