When referred to the output, the intercept point represents the point where the extrapolation of the linear region of the fundamental-power-output curve and the spurious power level curve intersect, when plotted on a log-log scale with output power as ordinate and input power as abscissa. The most common output intercept point is O IP₃, the output third order IP; in this case the spurious signal of interest is the third order intermodulation product. Other less common intercepts measure second order (harmonic) distortion level (IP₂), or higher product intermodulation level (e.g. IP₅ or IP₇).

Intercept points may also be referred to the input of a device. In this case, It represents the point the extrapolation of the linear region of the fundamental-power-input curve and the spurious power level curve intersect, when plotted on a log-log scale with output power as ordinate and input power as abscissa. Input intersect points can be derived by subtracting the device gain from the output intercept point value.