Calculate Maintenance Calories 

It's recommended to be in a daily deficit of 10-20% of your total energy expenditure (TEE). For example if your TEE from the above calculator is 2500 then you'll want to start by creating a calorie deficit of 250-500 calories. Meaning, you'll be eating 2,250-2000 calories a day. It's ideal to start slow and eventually work your way up to a larger deficit. 

To gain muscle, you must be in a calorie surplus. Muscle cannot be built from nothing, there has to be something for new tissue to be created/expanded. More calories equal muscle, but too many calories equal too much fat. When trying to maximize muscle gain and minimize fat gain, eating in a small surplus of about 10-15% of your total energy expenditure (TEE) is critical. For example, if your TEE is 3,000 calories, then you would want to eat 3,300-3,450 calories per day.

Some people are pretty happy with where their weight is but want to ensure they're eating enough. If you're goal is to maximize your performance in the gym, field, track or court then you should aim for the total energy expenditure (TDEE) number from the above calculator. Getting enough calories is key to maximizing performance. Too few calories and your workouts will suffer, too many and you'll start to gain weight.