30 BAD recommends 2500 for women 3000 for men.
80 10 10 has a formula and seems to promote calorie reduction if looking for weight loss. It may also recommend reducing calories by activity rather than starving yourself.
I found the method I've heard DR recommend for determining your what your carb intake per day should be: 10 grams of carbs per KG.
So 147 lbs. (my weight) = 66.68 KG. So I should be eating 667 grams of carbs per day. One day that I tracked I ate 756 g of carbs, so I have certainly been hitting that. That was 3332 calories.