Calc Kill La Kill - Satsuki confronts Berserker Ryuko

(http://imgur.com/G9R1nYK)
Satsuki and Berserker Ryuko clash, creating a huge explosion. In a previous calc, I put Honnouji Academy's grounds at being 410.32m in diameter.
1997 pixels = 410.32m
1 pixel = 410.32m/1997 = 0.205468202m
0.205468202m X 1010 = 207.522884m
0.205468202m X 1068 = 219.44004m
219.44004m/2 = 109.72002m

Volume as a cylinder.

V = πr^2h
= π X 109.72002^2 X 219.44004
= 8299224.31m^3

Density of air is 1.003kg/m^3.

M = 8299224.31 X 1.003
= 8324121.98kg

Finally, we just need two things. Firstly, a timeframe...
Timeframe is 21 frames.

T = 1s/24
= 41.6666667ms X 21
= 0.875000001s

T = 207.522884m/0.875000001s
= 237.16901m/s

...Secondly, kinetic energy.
KE = (0.5)mv^2
= (0.5) X 8324121.98 X 237.16901^2
= 2.34112348e11 joules
= 55.9541940726577 tons of TNT

Final Results
Satsuki & Berserker Ryuko clash = 55.954 tons of TNT