Learn The Math Behind the App

You have four variables:

• Total Calories Eaten — taken from Apple Health since the specified Start Date
• Start Date — configured in the settings / the day you want to start off grabbing calories from
• Max Calories Per Day (or Limit) — configured in the settings / the maximum calories per day you don’t want to exceed
• Current Date — equals the present date and time

From these variables, you derive:

• Days Since Start Date: $\text{Current Date} - \text{Start Date}$
• Calories Per Day (or Daily Average): $\frac{\text{Total Calories Eaten}}{\text{Days Since Start Date}}$
• Remaining Calories: $(\text{Max Calories Per Day} \times \text{Days Since Start Date}) - \text{Total Calories Eaten}$
• Time to $X$ Kcal Surplus: $\text{TargetDate}(X) - \text{Current Date}$, where

$$\text{TargetDate}(X) = \text{StartDate(midnight)} + \frac{X + \text{Total Calories Eaten}}{\text{Max Calories Per Day}} \text{ days}$$

Why does dividing calories by Max Calories Per Day give days? Unit cancellation:

$$\text{Calories} \div \frac{\text{Calories}}{\text{Day}} = \text{Calories} \times \frac{\text{Day}}{\text{Calories}} = \text{Days}$$

The calories cancel out, leaving the time it takes to accrue that many calories at your daily limit — the same way distance ÷ speed gives travel time.

So if we want to find out how long we have to wait until we can eat 250 calories when we’ve eaten 3,000 calories since the start date, which is 2 days ago (let’s say June 26, 2026), and the max calories per day is 1,600, then:

$$\text{TargetDate}(250) = \text{June 26, 2026 12:00 AM} + \frac{250 + 3000}{1600} \text{ days}$$ $$\text{TargetDate}(250) = \text{June 28, 2026 12:45 AM}$$

So if the Current Date is June 28, 2026 12:00 AM, Time to 250 Kcal Surplus would be 45 minutes.

That’s it.

Oh, and you can also enable an option to subtract Active Energy (also taken from Apple Health), and all that does is reduce your Total Calories Eaten by it, so all the dependent calculations immediately update.

Note on Remaining Calories:

• Please don’t eat 10,000 calories in a day, because that’s what your remaining says.
• This app is about weight loss.
• If your iPhone is telling you that you burnt a million calories, and you’re still overweight, you may need to double-check your Health data for accuracy.