19 lbs

Blast yields are compared to their approximate explosive power equivalent to TNT. A 1 Megaton explosion is equivalent to the explosive power of approximately 1 million tons of TNT.

A 1 kiloton nuclear blast has the equivalent explosive force of detonating 1 kilotons of TNT.

There is no "nominal" atomic bomb, their yields can vary from less than 100 tons TNT equivalent to nearly 1 megaton TNT equivalent. Therefore there is no single meaningful answer to this question.

Hydrogen bombs have no upper limit for yield!

The Whistling Phantom.