The frequency of the third harmonic is calculated by taking the foundational fundamental frequency of a wave or oscillating system and multiplying that value by the integer three. For instance, if an alternating current power distribution network or an acoustic musical instrument operates with a fundamental frequency of 50 Hertz, the frequency of its third harmonic is 150 Hertz. Similarly, for a standard 60 Hertz North American electrical utility grid, the third harmonic frequency is precisely 180 Hertz. This predictable linear relationship applies universally across acoustics, signal processing, and electrical power engineering whenever nonlinear system behaviors generate higher-order periodic overtones.