Penetration
From the Multicrew Tank Combat wiki
Contents
Penetration is how much armour a round can get through. The figure on a shell page is the best case: point blank against a flat plate. This page covers what takes away from it.
Distance
Solid shot loses penetration as it flies. That covers AP, APHE, APCR, APDS and APFSDS. HEAT, HE and missiles keep all of their penetration at any range.
How quickly a round loses it differs from round to round. The Penetration table on each shell page gives the figure at 100 m, 500 m, 1,000 m and 2,000 m. For example, 
M829A3 still has 94% of its penetration at 2,000 m, while 
BR-471 is down to 79% at 1,000 m.
The range counts the whole flight, including any ricochet on the way.
Angle penalty
A steep hit makes the armour thicker (see Line-of-sight thickness). For solid shot it also costs the round some of its own penetration. The penalty stops getting worse past 75°. HEAT and HE pay no angle penalty.
Long-rod APFSDS is the exception among solid shot. It loses nothing to the slope, and even gains a little: about 17% at 60°. The gain is the angle term of the Lanz-Odermatt formula, described under How the figures are calculated.
Overmatch
A full-calibre AP or APHE shell that is wide compared with the plate it hits loses slightly less penetration to the angle. The effect is small, and it only exists at angles under 40°. The reverse also holds: a plate that is thick compared with the shell makes the angle penalty worse.
Going through more than one plate
A round keeps whatever penetration the plate did not use up. For example, a shell with 300 mm that goes through 200 mm of armour flat on has 100 mm left for the next thing in its path.
If the plate took more than 75% of its penetration, the round slows down as well.
Walls and terrain
Walls, buildings and terrain count as armour: 30 mm for every metre of material. Only solid shot goes through them, including machine gun bullets. Every other round stops at the first wall.
A wall or building never counts as more than about 54 mm, however thick it is.
How the figures are calculated
The penetration of a round comes from the real projectile. Which method is used depends on the kind of round.
| Round | Method |
|---|---|
| Full-calibre AP and APHE | De Marre formula |
| APFSDS | Lanz-Odermatt formula |
| HEAT warheads and missiles | Published figures for the real weapon |
| HE | Worked out from the amount of explosive the shell holds |
De Marre
The De Marre formula dates from 1886 and estimates what a full-calibre steel shell goes through from its muzzle velocity, mass and calibre:
penetration = (velocity ÷ K)1.43 × shell mass0.71 ÷ calibre1.07
K is a constant for the quality of the shell and of the armour. A heavier or faster shell goes through more, and a wider shell of the same mass goes through less. The War Thunder wiki has a longer explanation of the formula.
Lanz-Odermatt
A long-rod penetrator does not behave like a full-calibre shell, and De Marre gives wrong answers for it. APFSDS uses the Lanz-Odermatt formula instead, which was fitted to firing trials of tungsten and depleted uranium rods:
penetration = a × rod length × cos(angle)−0.225 × √(rod density ÷ armour density) × exp(−(s ÷ velocity)2)
The value a depends on how long the rod is for its width. The value s depends on the rod material and the hardness of the armour. The negative power on the angle is what gives APFSDS its gain against sloped plates. You can try the formula with your own numbers in the Lanz-Odermatt calculator on longrods.ch.