Free scheduling tool
Intermittent Fasting Calculator
Choose how many hours you want to go without food and when your first meal is. The calculator shows the eating window, the fast and the meal times in between.
Worked example
A 16:8 schedule with a first meal at 12:00 pm gives an eating window from 12:00 pm to 8:00 pm, then 16 hours without food until 12:00 pm the next day.
Plan your eating window
The result below starts from the example's numbers. Change any field and it updates as you type.
Track this target every day
Use the number above as your daily goal in CalorTracker, then log meals by photo, voice or text and see where your day stands against it. Free to start, no card needed to explore.
Results are estimates from published formulas, not medical advice. Your own body can sit above or below them.
Where the formulas come from, and how we check them: how we calculate.
What this calculator does
It is a clock. A schedule such as 16:8 means 16 hours without food and an 8-hour window in which you eat. Give it your first meal time and it adds the window to find when eating stops, when the fast starts and when it ends the next morning, and it spaces your meals evenly through the window. The last meal starts an hour before the window closes, so there is time to finish it.
The schedules
- 12:12, 12 hours fasting and a 12-hour window.
- 14:10, 14 and 10.
- 16:8, 16 and 8.
- 18:6, 18 and 6.
- 20:4, 20 and 4.
The schedules differ only in the length of the window. This page makes no claim that any of them is healthier or leads to more weight loss. If you want a calorie target to eat inside the window, the calorie calculator gives one, and it does not depend on when you eat.
Who should check first
Skipping meals is not suitable for everyone. Talk to a doctor or registered dietitian before you start if you are under 18, pregnant or breastfeeding, have diabetes or another medical condition, take medication that has to be taken with food, or have ever had an eating disorder.