For standard ECON descent in B744: (current Mach into 290):
(3 * Height + x ) +/- 1/3 of H/W or T/W component.
(where x decreases from 20 at FL400 to 10 at 10,000')
Eg: From FL400 with 60kt H/W: (3 * 40) + 20 - 20 = 120NM
From FL300 with 30kt T/W: (3 * 30) + 20 + 10 = 120NM
You can obviously interpolate for other altitudes (eg FL350) and these are only ballpark figures but once you get a bit lower use:
20,000': 80nm (Hard Gate)
10,000': 40nm (Hard Gate)
5,000': 20nm 250KTS (Hard Gate)
LH