This may be a question several of you have asked, even I have. Now, I need help from you guys for this one, so you can comment on both Godzilla's weakest and strongest use of Atomic Breath. this is because I've never actually seen it myself (yeah...).

In a nutshell, this is what I need from you guys:

2 times  when Atomic Breath was used, one Weakest and one Strongest

I need each of the above for every part of the franchise( Showa, Heisei, Millenium, and Final Wars)

How many buildings it destroyed or how big the general explosion was(compared to Godzilla)

And Finally

How big the City/Biome/State/Location is in that moment.

Thanks! I'll edit this when you have posted all of the above, and I will put in the names of those who I picked/ who had the most realistic or accurate comments.

                                                                                                                          Naku Mun

By:Ghidorahnumber1: if Heisei has the power of a small atomic bomb, then that would equal 1 kiloton of TNT. and with Showa's ability to burn, I'd guess about 0.3 kilotons. Thanks man

By: Shodai Goro: if in Final Wars, Godzilla's breath can kill Kaiju, than I'd think this. along with the sheer size of the monster and the resistance to such weapons, Godzilla has the ability to fire a beam equivalent to 10 or 13 Kilotons of TNT. Thanks!

Final Update: I've come to these conclusions, thanks to the people above, and NukeMap Classic

Godzilla (The Original Movie): 0.1 KT

Godzilla Showa Series: 0.3 to 0.5 KT

Godzilla Heisei Series: 1 to 3 KT

Godzilla Millenium Series (And/Or Final Wars): 10 to 13 KT (or 17 max)

(New/Legendary) Godzilla 2014: 37 to 50 KT (most likely 80 KT if he can charge it like in Millenium)