Not just an ILS but also in a non-precision approach. ICAO Pans-Ops states:
5.3.2 Determination of the descent gradient for a non-precision approach with FAF
The descent gradient (g) for a non-precision approach with FAF is computed using the equation: g = h/d. The values for h and d are defined as follows:
a) For a straight-in approach use:
d = the horizontal distance from the FAF to the threshold (Cat H, LDAH); and
h = the vertical distance between the altitude/height over the FAF and the elevation 15 m (50 ft) over the threshold.