I’ve been looking around at different sources and methods and I get results that aren’t similar. Anyone have a good proven method?
Trial and error is the best way, but even that may be off.
I would look at various TDEE calculators and get an average. If your average maintenance is 2,800 cals, I would eat there for a week. Weigh yourself first thing Sunday morning after you use the bathroom, eat 2,800 cals every day for the week, and then weigh yourself the following Sunday after you use the bathroom, before you eat or drink anything.
If you gain weight, you know 2,800 is not maintenance, but if you lose weight, you are under that. if your weight stays the same, you're there. I would not worry if your weight is no 100% percent the same. There are other variables that dictate what you will weigh in at. If you weigh in at 180 pounds and eat 2,800 cals then a week later weight 179.8 or 180.2, you are at maintenance. If you are well over or under, adjust.