Only adding muscle will increase your bmr, not fat. The calculators are an estimate. Without body fat %, you can't calculate w/complete accuracy. If you want to pick apart my 863 calories, point out how you'd have to decrease physical activity as well for it to be accurate bc as you carry the extra weight, you'll expend more energy doing the same amount of physical activity. So if you don't live a sedentary lifestyle, you'll need more than 863. A 600lb person for instance burns a ton of calories just walking. But if you already sit and lay around all day, 863 will be about enough. If it's not enough wait 5 1/2 or 6 years instead. Any increase in calories burned will be covered by that. Unless you're like an on foot mailman or something.