The maximum thickness of the T80U front turret armor is reported to be 815mm thick reaching ~920mm near the gun in the "weakened zone". The insert is probably similar in size to the T90 with ~380mm LOS insert thickness suggested.
The turret is cast with almost half insert which is probably AD90 mounted on STEF. The KE value of this combo is probably (0.9+0.41)/2 = 0.65 and HEAT value of (1.5+0.55)/2=1.025. Thus the effectiveness is 0.78 KE and 1.02 HEAT around the front turret and 0.66 KE and 0.775 HEAT around the rest of the turret. In other words the 815mm front turret LOS thickness translates into 0.78 x 815 or 64cm KE resistance while the mantle reaches ~83cm and the sloping walls reach 56cm KE resistance. However the 'free edge effect' should reduce the KE values below these figures, the area near the gun would go down 0.6 to 50cm KE, while the 815mm section should be ~0.9 x 64cm or 57cm, and the main walls would be ~ 0.95 times 56cm or 53cm. So the weakened area is around 5051cm while the main walls are 5357cm KE. The HEAT values should be 720815 x 1.02 or ~7383cm along the main walls.
Kontakt5 coverage seems to be about 60%.
Upper front turret is 5cm cast plus 5cm STEF at ~7778°.
Glacis is 235mm thick with three steel plates of varing hardness and one layer of STEF. If we assume all plates are 5cm with one of the steel plates semihardened steel and the STEF is 5.5cm thick,  The steel would equal 10 + 5 x 1.34 or 16.7cm plus the STEF, which has a KE resistance of 0.41 and HEAT value of 0.55, thus the total resistance is 18.9cm KE and 19.7cm HEAT @ 67° or 49.7cm KE and 52cm HEAT .But a 3cm hard steel plate was added in the 80s boosting the KE resistance by 1.34 x 3 ÷ 0.38; or 60cm KE & 63cm HEAT. With K5 thats 78±2cm KE & 108± 5cm HEAT.
Lower hull is 810cm at 64° = LOS thickness of 0.438 or 1723cm KE armor, plus a rubber flap that hangs from the hull nose and provides a basic spaced armor for HEAT warheads. Since the rubber flap is likely to slide against the penetrating HEAT Jet it probably offers about 79cm plus the effect of standoff [6cm HEAT] for a total of about 3038cm HEAT armor. The additional KE resistance is maybe +1cm due to projectile deflection or yaw.
~8090cm LOS cast mantle x 0.60.7^{1} = 5456cm KE & 8090cm HEAT  
81.5cm LOS x 0.78 [Cast/STEF/AD90] = 64cm x ~0.9^{1} = 57cm plus K5 = 72±2cm KE
81.5cm LOS x 1.02 [Cast/STEF/AD90] = 83cm plus K5 = 128±4cm HEAT 

7072cm LOS x 0.78 [Cast/STEF/AD90] = 56cm x 0.95^{1} = 53 plus K5 = 71±2cm KE^{2}
7072cm LOS x 1.02 [Cast/STEF/AD90] = 72cm plus K5 = 118±4cm HEAT^{2} 

4448cm LOS x 0.66 [Steel/STB] = 2932cm KE plus K5 where present = 48±6cm KE
4448cm LOS x 0.77 [Steel/STB] = 3437cm HEAT plus K5 where present = 70±16cm HEAT 

[10 + 8 x 1.34 + 5.5 x 0.41] / 0.38_{3} = ~60cm KE plus K5 = 78±2cm KE
[10 + 8 x 1.3 + 5.5 x 0.55] / 0.38_{3} = ~63cm HEAT plus K5 = 108±4cm HEAT 

1824cm KE and 3038cm HEAT  
Side turret ranges from 4060cm thick near front thinning to ~ 1520cm around back. This is probably half and half cast/STEF thus the KE armor is 0.66 while the HEAT armor is 0.77. The effective KE armor ranges from 40cm narrowing quickly to 26cm and 1013cm around back. The HEAT armor ranges from 4631cm near the front down to 1512cm Around back. In the side and rear turret are mounted external storage boxes ~50cm thick that will offer a modicum of spaced armor, this may amount to an additonal ~1315cm HEAT armor. Additionally K5 is mounted around the front side of the turret.  
The side hull is 6cm thick rolled steel but the lower side hull around the wheels is probably only 2cm thick; side skirts add 25 mm thick reinforced rubber [with steel?] plate plus 60cm airgap increasing the HEAT armor by about 1517cm against 2nd gen and 2628cm against 1st gen warheads. This rubber skirting is unlikely to add more than 1cm to the KE side armor, due to deflection. The fuel tanks along the sponsons should add 65cm x 0.1 KE and 0.3 HEAT or an additional 67cm KE and ~ 20cm HEAT armor. Over the front half of the side hull NERA is mounted which probably adds ~30cm HEAT and a couple of cm KE resistance.  
The rear armor is unlikely to be more than 4cm but fuel tanks mounted there could offer 0.1 to 0.15 Te resistance to APFSDS and 0.34 resistance to HEAT. The HEAT armor would range from 34cm to as much as 18cm additional HEAT armor. 
^{1}   adjustment for freeedge effect 
^{2}   a substantial portion of this projection on the right side of T80U is not covered by ERA due to mounting of L4 IR searchlight; an area both on the left and right is not covered on T80UK because of Shtora emitters. In these areas, instead of K5 assume additional <1cm KE and ~5cm HEAT protection. T80U(M) is free from this disadvantage. 
^{3}   adjustment for LOS due to angle 
This page is © 2000 Sauron's Creations,
with major contributions by Paul Lakowski.