Required Deficit for a day is calculated as the total number of "deficit" calories left to lose to reach your target weight divided by the number of days remaining until the target date.
The total number of "deficit" calories left to lose is calculated assuming you need to lose 3,500 calories to lose a pound of weight. If your goal is to lose 50 lb, for example, then the total calorie deficit is 3,500 * 50 = 175,000 calories.
The 175,000 number is subsequently divided by the number of days left until your Target Date. So, let's say you set up to lose 50 lb by the end of the year - you will have 365 days left at Jan 1. So 175,000 divided by 365 will be approximately 480 Required Deficit calories for the day.
In case your weight does not change at all - the Required Deficit number will increase the closer you are to the Target Date, thus pushing you to lose weight faster to reach your goal.
