How do you figure out macros when you have 100 lbs or more to loose?

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Hi, This is my first post. I'm trying to figure out how to calculate my macronutrient needs, I have read a few articles but find that when I calculate by their formulas that I would either have an extremely high amount of calories, or under 1,800 calories, which seems low for someone of my weight considering I am exercising. does anyone have any suggestions? Thanks.