Requested by User:BlackDarkness679 here
The mountain in the background is 205 pixels, while the screen is 715 pixels.
Anglesizing is a matter of 2*atan(tan(70/2 deg)*(object height/panel height)), in this case, 2*atan(tan(70/2 deg)*(205/715)) makes for 0.396250146 radians. To convert to degrees, it's rads*180°/π, so, 0.396250146*180°/π makes for 22.7034609972 degrees.
Mountains are at least 610 meters tall, so, putting everything into the anglesize calculator gets 1519.2 meters.
1519.2^3×((27136×1.37895+8649)^(1/2)/13568-93/13568)^2 makes for...
281793.110179 Tons, 281.793110179 Kilotons, Large Town level
You could probably also calc beam speed from how high up the satellite is and the fact that GUN Jack had to take cover before it hit, but I'd probably have to do a curvature calc using the shot we get of the satellite itself or some assumed distance which I'm too lazy for both of (Especially considering JACK could feasibly detect the beam from when it was in the clouds, giving him a bit more time to work with)
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Then again, it doesn't really look like it goes to the mountains, since they're still kinda around. A more reliable method would be using the height of the clouds.
Cumuluses are a mile in the air, 1609.34 meters, dividing by 2 gets a radius of 804.67 meters
So, 804.67^3×((27136×1.37895+8649)^(1/2)/13568-93/13568)^2 makes for...
41873.4693981 Tons, 41.8734693981 Kilotons, Town level
Do kinda want to know how battle royale calced this to 1.05 Megatons with Near Total Fatalities, but they didn't show their math for me to check, so sucks to be them.