Well I was in Gepraphy today, and it's boring as f**k because we 100 minute lessons, but I managed to listen when my Geography teacher told me about supervolcanoes.
I decided to look up some more stuff about it and I stumbled upon this website.
A column of ash spewed 21 miles (34 kilometers) into the atmosphere, opening like an umbrella to form a cloud 249 miles (400 km) across.
According to here the eruption was some ten times larger than the 1980 eruption of Mount St. Helens.
St Helen's yield is 24 Megatons, so the yield of Mount Pinatubo would be 240 Megatons.
200 x 200 = 40000
40000 x pi = 125663.706
Lina has already worked out the rest of it here, so we'll part of his.
1.258e9 / 125663.706 = 10010.8459
10010.8459 x 240 = 2402603.02 Megatons or 2.40260302 Teratons.
Small Country level
To Anyone that is confused as to what exactly I am calcing, the calc is to work out the yield of a volcano that surrounded the entire Demon work in darkness, I used the amount of ash from real life volcano's to calc this.