If you are looking to lose weight, gain weight, maintain your weight, build muscle etc then you need to know how much to eat to achieve this goal. I have used several calculators and a variety of formulas and this calculator (and formula it uses) remains my favorite. It is super detailed and gives you descriptions on each of the exercise intensities. I would recommend doing a calculation for an exercise day and a non-exercise day so you can adjust your calories in your food-tracker app to reflect the difference in activity.
1 pound of body fat is equal to 3,400 calories, so a weight loss journey is not something that happens overnight. The MAXIMUM caloric deficit from the total daily expenditure you calculate should be 1,000 calories, otherwise you will risk catabolizing the muscle you have worked so hard for as well as drastically slowing your metabolism. A 1,000 calorie deficit per day will equate to about 2 pounds of weight loss per week. A 500 calorie deficit should cause a 1 pound weight loss per week. Keep in mind, it takes roughly 3 weeks for your body to adapt to whatever changes you make, so stick to it for 3 weeks before you try to change up the plan!
Here is an example of the calculator all filled out:
Source: MJ Fitnatic