[MarkSheppard]

So I discovered a 1968 article by Richard M. Ogorkiewicz titled "Thoughts on...FUTURE TANK DESIGNS" in ARMOR magazine (the US Armor community's official journal).

It had a simple equation which with some modification by me, proved to be pretty good (eyeball accuracy wise) for predicting protection for weight of a conventional tank:

T = ( E * W ) * A

Where:

T = Horizontal thickness of frontal hull armor in millimeters.

E = Efficiency of hull design.

Tanks with straight sides will have lower E numbers, while tanks with excellent sloping will have higher E numbers.

Rough E#'s:
Tiger I (2)
US WWII (2.75 to 3)
Tiger II (3)
T-54 Hull (4)
T-54 Turret and IS-7 Hull/Turret (5.5)

W = Weight of tank in metric tons.

A = Aspect Correction Factor (1.0 for front, 0.65 for side)