How many calories should you eat to gain weight and build muscle?
This will depend on your weight in pounds. To maintain your current weight, you only need to consume about 10 calories per pound. For example, a 125 lb person would need to eat 1250 calories just to maintain their current weight. In order to gain weight, you need to consume more calories then what your body requires. A basic weight gain formula is to consume 15 calories per pound of weight. So the same 125 lb person would need to consume 1875 calories. Assuming that you have a fast metabolism (which is the case for most people who want to gain weight), you can overshoot this number a bit, and go on a 2000 calorie diet. If you find that you are not gaining weight after a few weeks, add 300-500 calories.