A couple weeks ago, I published Watts. Here is some of the math behind it -
Confused by so many units? Make sense via Saul Griffith's presentation (link in older post).


Note – In context of food a calorie generally refers to kilo-calorie. Some numbers may not be recent. If you do find some glaring mistake, do comment.

Image source - IEA in a presentation by Margot Gerritsen