Some things you weigh.
Some things you weigh once, measure in some other more convenient form (e.g. 5tbsp of special flakes are about 40g, 4tbsp of bran flakes are about 40g, 3tbsp of oats are about 40g), then make a note.
Other things you just have to guess.
I know – from years of dieting – that a low calorie thing to order in a curry house is tandoori chicken (no sauce) with plain rice and a vegetable side. I ordered this. I shared the rice and the side with R. BUT what of the many things labelled “Tandoori Chicken” in MyFitnessPal correspond to tandoori chicken as ordered in the Light of Asia? There are hundreds. You can cut it down by adding the word “Generic” to the search (top tip) but it doesn’t really help.
Not a clue. So it’s going to be an estimate.
(It is of course always going to be an estimate, even in restaurants where they provide you with calories on the menu; it’s not the case that every Wetherspoons small Nachos is exactly 657 Calories. Menus with nutritional info are probably a bit more accurate than just guessing though. One of the reasons I’m not a huge fan of calorie counting is that I have a tendency to become a little obsessed about this kind of thing…)
Also: every now and then, MyFitnessPal makes some strange assumptions about quantities. It’s worth double checking, particularly on recipe import. See below for its interpretation of “1 onion”: