In Chapter 56 of My Hero Academia: Vigilinates, Knuckleduster decided to detonate a bomb placed in a building in order to throw off Number 6, with the aftermath being shown at the beginning of Chapter 57.
Iwao has a height of 6'1", which is 185 cm or 1.85 metres.
Knuckleduster: 52 px (1.85 m) which when divided equals an unit rate of one metre for every 28.11 pixels.
Radius of AoE: 153 px / 28.11 px = 5.44 m.
Average floor/ceiling height for residential buildings is 7.5 feet or 2.29 metres.
Finding Volume & Energy
I assume we can use cylindrical volume for the volume of the amount of floor that he destroyed, seeing as how the area of destruction is in a circular shape (the debris, the dust, and the amount of floor that isn't destroyed all align with a shape that is a circle). Plugging these values into the cylinder calculator, we get 212.903 m^3 which is 212903000 cc.
Now that we have the volume, we can find the energy. Floors are typically made of concrete, or so I'm told, and the debris that is caused by this happens to be very large, so it's a definite Fragmentation situation.
The fragmentation of concrete is 6 J/cc
KE: 212903000 x 6 = 1277418000 Joules; 0.31 Tons of TNT (Building level)
But, since Knuckleduster say that he took out three entire floors with this explosion, we can safely multiply the KE by 3x to get the final result.
Total KE for Bombs: 1277418000 x 3 = 3832254000 Joules; 0.92 Tons of TNT (Building level)
Energy for Building Destruction Feat
Oh, but there is more. At the end of the chapter, the building is revealed to have been reduced to rubble, which means either their clash caused this, Knuckleduster used the bombs to do this, or they fought and destroyed the building, Dragon Ball style. But either way, it's destroyed.
There is a lot of debris there, so it could be Fragmentation or Violent Fragmentation.
The Frag. of concrete is 6 J/cc
The Violent Frag. of concrete is 20 J/cc
Frag.: 859100000 x 6 = 5154600000 Joules; 1.23 Tons of TNT (Building level+)
Violent Frag.: 859100000 x 20 = 17182000000 Joules; 4.11 Tons of TNT (Large Building level)
3832254000 Joules; 0.92 Tons of TNT (Building level)
The Building's Destruction
Low-End: 5154600000 Joules; 1.23 Tons of TNT (Building level+)
High-End: 17182000000 Joules; 4.11 Tons of TNT (Large Building level)
These may scale to Knuckleduster's AP and/or Durability, or may not. I may calculate the feat where Number 6 crosses 250 metres faster than Knuckleduster could process, and where he runs to Knuckleduster before he could shoot him with a rifle.