Captain Tagon: How big an explosion are we talking about?
Petey: Since we know the mass of the bomb, the energy deposited on targets can be reasonably approximated with ancient, easily-comprehended mathematics.

Einstein's math will give you the overall yield, attenuation over distance can be figured with the inverse-square rule, and spherical distribution of energy is a function of Pi.
Tagon: Pi? You mean Corporal Pibald had something to do with this?
Petey: Pi is the irrational ratio between the diameter and the circum
Tagon: Oh, I know he's irrational. I just thought Doctor Bunnigus had him medicated.