Nuclear blast zone damage estimator. Something to have fun with over coffee. NUKEMAP by Alex Wellerstein The ones we dropped on Japan were about 15 kilotons - which doesn't do as much damage as you might think. The biggest one ever the was Tsar Bomba @ 50+ megatons that the Commies dropped. Described very well in Wiki as "The Tsar Bomba is the single most physically powerful device ever deployed on Earth"