Reread more accurately things and edited my post.
Name, Size, Strength (Modifier), range.
Storms Giants, Huge, 39 (+14), no rock throwing*.
Clouds Giants, Huge, 35 (+12), 140 ft.
Fire Giants, Large, 31 (+10), 120 ft.
Frost Giants, Large, 29 (+9), 120.
Stone Giants, Large, 27 (+8), 180 ft. (but they have some special bonus)
Hill Giants, Large, 25 (+7), 120 ft.
Let's take more examples. MC: Monsters of Faerûn:
Fog giant, Huge, 29 (+9), 140 ft.
Phaerlin Giant, Huge, 21 (+5, what a wussy), no rock throwing.
Tome of Horrors:
Sand Giant, Huge, 37 (+13), no rock throwing.
Wood Giant, Large, 21 (+5), no rock throwing.
Deities & Demigods (thanks Boz):
Lesser Cyclopes, Large, 27 (+8), 140 ft.
Greater Cyclopes, Huge, 33 (+11), 140 ft.
Monster Manual 2:
Forest Giants, Huge, 33 (+11), 120 ft.
Sun Giants, Huge, 37 (+13), 120 ft.
Ocean Giants, Huge, 39 (+14), 120 ft.
Mountain Giants, Colossal, 43 (+16), range not precised, but can fling enemies "up to 120 ft" -- this does seem wrong, by the way, as lesser giants can fling rocks up to 5 times this (600 ft.) at least.
* I read the MM too fast the other day, storm giants don't throw rocks, but they have a bow with 180 ft. range increment.
If the Lesser Cyclopes only had 120 ft. range increment, and if the Forest, Sun, and Ocean giants had 140 ft., then it would have been dependent on size, unless special affinity like the stone giants.
If a formula was to be extrapolated, I would say to use 100 ft. plus 20 ft. by size category above Medium.