Macros and counting

Hi!

What is the best way to compute macro homemade meals?

For example if I want to make something like salad dressing or coconut rice, but I don’t know the serving size(s), how do I do this?

I want to be able to input all of my ingredients without knowing the serving size and then input the amount I take in MFP or some other site and have it calculated it for me. Sometimes I don’t know how much I’m going to take and I don’t know how much it’s going to make!