Many people wrongly assume that the BMR = maintenance calories. That is not so. BMR (basal metabolic rate) is the amount of calories that your body needs just to function. That means to sustain all the vital organs like the heart and the basic functions like breathing.
Most people, besides breathing and staying at rest, also do other things during the day, like walking and sometimes even being active. 🙂
All these activities require a greater expenditure of calories than the BMR. So in order to change your weight you need to find what your MAINTENANCE calories are. Maintenance calories are your BMR calories + the amount of calories that you expend throughout the day on going around doing your daily activities (for example walking or doing sports).
If your goal is to gain weight, then you should eat more calories than your maintenance calories. For people that are trying to lose weight, they should first calculate their BMR and their maintenance calories. After that they need to eat less calories than their maintenance calories, but still more than their BMR.
Here are two calculators that you can use to calculate your BMR and your maintenance calories:
Read more: How to gain weight