u/Few-Tip2670

I switched to chronometer about a week ago and I like it but there are some things that I don't understand. What is a KCAL as compared to a calorie? I enter my custom calorie intake for the day and it instantly changes, why? The whole Macro thing is lost on me so I'm kind of taking it slow on that. I'm comparing the results of the search for foods to MFP and they are pretty similar. I've got a pretty good idea of the app but could use a little help. Thanks to all.