How does the app calculate calorie intake?

[Sbfowler2017]

I have my settings for a 500 calorie deficit, however, it is showing I only have 839 calories left to eat today, and I have not logged any food. Shouldn't it show 1500 calories left if nothing has been logged?

Moderator Edit: Clarified Subject.

[MarcoGFitbit]

Hello @Sbfowler2017, I hope you're doing well, thanks for joining the Fitbit Community. 

I have moved your post from the Flex boards to the iOS boards to keep the Community organized and to give your post the chance to get more attention.

When you start a food plan, depending on the aggressiveness of the plan you will only be allowed to consume a determined amount of calories, if you consume more calories than allowed you will be able to see these calories were "over" your total. Please note that the Daily Calorie Estimate uses your average activity to give you an estimate of how many calories you should eat for the whole day to meet your weight goal. This updates throughout the day if you are more or less active than usual. As you log food during the day, the calories you can still eat will update, you will be in your goal zone as long as you are within 50 calories of your deficit goal for the current time of day.

Daily Calorie Estimate tile.

The Daily Calorie Estimate  is an estimate of the total calories you can eat for the whole day, taking your BMR, Activity Calories, Food Plan deficit, and whether you're on a Personalized or Sedentary plan into account. The Calories In vs Out gauge, on the other hand, is specific to the current time of day, and includes the fraction of your food plan deficit that you should have earned by that time of day as well as the calories you've actually burned in the same time period. If you think of the Calories In vs Out gauge as an "Eatometer," showing how fast you're consuming your daily calories, it may make understanding the difference easier.

Calories In vs. Out tileFor example, consider someone who eats a big breakfast early in the morning. Even on the Sedentary plan, they may already have a Daily Calorie Estimate of 1300 calories or more first thing in the morning, reflecting their entire daily BMR, so eating a 1000-calorie breakfast would show that they still had 300 calories left to eat for the day.

The Calories In vs Out gauge, however, only gives credit for calories actually burned so far for the day. At 6AM, they may have burned only a few hundred calories BMR while sleeping, plus a few activity calories for stumbling to the bathroom, brushing their teeth, and making their way to the breakfast table. In addition, since it's 6AM, 25% of the day is gone, which means that the gauge needs to hold 25% of their daily deficit in reserve. If they're on the 500-calorie deficit plan, that's another 125 calories to be accounted for. So it's quite reasonable for the Daily Calorie Estimate to show 300 calories left to eat for the day, while the "Eatometer" is WAY over in the red zone, shouting "Slow Down, you're eating too fast!" Early in the day, that's not a problem; later in the day, you should be paying close attention.

To summarize, the Daily Calorie Estimate will often tell you that you have more calories available to eat, even if you're "over budget" at the current time. It's okay to be "over budget" early in the day, since it's better to eat earlier rather than later, but be careful about running over the Daily Calorie Estimate for the day unless you have a lot more exercise planned.

Also remember that the Daily Calorie Estimate will increase throughout the day as activities burn calories, so that 1300 morning estimate may turn into 2500 or more by the end of the day. Don't assume that the first number you see in the morning is your final daily food budget, unless you're planning to lay in bed all day.

I hope this solves your inquiries, if there's anything else I can do for you, please feel free to reply.