Think the Maus had thick armor?

Here is an interesting list of relative protection based on effective armor protection (as if millimeters of hardened steel plate).

Protection:

M1- 400 vs KE 600 vs HEAT

M1A1- 450 vs KE 700 vs HEAT

M1A1HA- 600 vs KE 1150 vs HEAT

Leopard 2A4 - 700 vs KE 1000 vs HEAT

M1A2- 760 vs KE 1400 vs HEAT

Lacrec- 800 vs KE 1600 vs HEAT

M1A2SEP- 840 vs KE 1400 vs HEAT

Leopard 2A5- 870 vs KE 1500 vs HEAT

Challanger 2- 960 vs KE 1700 vs HEAT

Leo 2A6 may be as high as 1000mm vs KE.

T-72B - 530 vs KE 620 vs HEAT

T-72BV- 580 vs KE 1120 vs HEAT

T-80B- 550 vs KE 650 vs HEAT

T-80BV- 600 vs KE 1150 vs HEAT

T-72BM- 780 vs KE 1220 vs HEAT

T-80U- 820 vs KE 1350 vs HEAT

T-90- 1000 vs KE 1600 vs HEAT

Really amazing how much technology has improved protection and this is ONLY the passive portion!