What would be the destructive effects of a gigaton nuclear warhead?

Question

What would be the estimated figures?

Be sure to mention the blast radius size.

Answer 1

There's a formula for that. I'm just gonna WAG it, though, and say everyone above ground in Ohio dies if it goes off in Columbus. A thousand one megaton bombs would destroy every city in the US, though. That's why they don't make them so big. It's more efficient to have many smaller ones.