Knowing your TDEE allows you to plan your workouts based on your goals. If your goal is weight loss, you might want to create a calorie deficit by doing more cardio. If you want to gain muscle mass, you might want to increase your calories and add strength training. For example, you might split your week into strength training days and cardio days, using the 3-on-1 principle: three days of strength training and one day of cardio.