Fasting Window Calculator
Tell it when you last ate, pick your protocol, and it shows you exactly when your fast ends and when your eating window closes.
Your fasting window
Fast started
8:00 PM
Fast ends — eat from here
12:00 PM
Eating window closes
8:00 PM
Fast for 16 hours, eat within a 8-hour window.
Which protocol should I choose?
12:12
Fast 12 hours, eat for 12. A gentle starting point — suits almost everyone.
14:10
Fast 14 hours, eat for 10. A popular step up that fits a normal schedule.
16:8
Fast 16 hours, eat for 8. The most researched and widely used protocol.
18:6
Fast 18 hours, eat for 6. For those who want deeper metabolic benefits.
20:4
Fast 20 hours, eat for 4. An advanced approach — not for beginners.
OMAD
One meal a day — 23 hours fasting. Only for experienced fasters.
Want the full picture?
The calculator tells you when to fast. The book tells you how — what to eat, how to handle hunger, and how to build a habit that sticks.
Get the Book →