When I'm tracking my meals I like to keep the math simple. Every label that you look at is going to be a little bit different one's going to tell you it's measuring a serving, another is going to tell you it's a cup, another's a half cup, another's a quarter cup, one's a teaspoon, or an ounce. That's just too much trouble.
The simple solution is switched to grams. You don't need to understand grams. You just need to be able to put it on the scale have your scale set to grams and enter the number it gives you. Everything converts over to grams. It's really simple.
What if you're mixing ingredients, then what, well I just made a batch of my three bean salsa, or spicy three bean soup, whatever you want to call it. Now I could take all the labels add everything up do some fancy math and try to figure out how many calories are in whatever but why bother. So in this case I had pinto beans, black beans,refried beans and salsa. The black beans had the highest number of carbs, fiber and calories so I'm just calling it black beans. I put three scoops into a bowl. My scale told me that was 200 g so I tell my calorie counter I had 200 g of black beans. The reality is the calories and carbs that I had were less than what was entered I'd rather them be less than more and it's not so dramatically less that it really makes a difference as far as my belly is concerned because it's less so simple math.