[gvkv]

Well done!

Plain and easy to understand interface and excellent use of colour and space. Two suggestions:

1. While I doubt it'll be used very much, consider adding calories for completeness if nothing else:

  1000 kcal -> joules

or

  1000 Cal -> joules

You might also throw in cal for just for fun[1]!

2. Change Variables to Constants. I think this is more in keeping with standard jargon.

[1]: cal is based on the gram while Cal or kcal is based on the kilogram.

[sharkdp]

Thank you for the feedback!

1. Yes, I'll definitely add calories, good suggestion.

2. Yes, that's probably a good idea. I should distinguish constants and (user-defined) variables.

[sharkdp]

calories are supported now.