Intermittent Fasting Calculator
Enter your eating window start time and IF protocol to instantly see when to stop eating, when your fast ends, and when your next eating window opens.
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Your Fasting Schedule
Protocol Reference
| Protocol | Fasting | Eating | Description |
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Intermittent Fasting Basics
How Intermittent Fasting Works
Intermittent fasting restricts when you eat, not necessarily what you eat. During the eating window, you consume all your daily calories. During the fasting window, only zero-calorie drinks (water, black coffee, plain tea) are allowed. Research suggests IF may improve insulin sensitivity, support weight management, and simplify meal planning.
Choosing a Protocol
16:8 is the best starting point for most people — flexible enough to accommodate a social life. 18:6 and 20:4 are more aggressive and may suit people who are already comfortable with 16:8. OMAD (23:1) is the strictest form and is not recommended without medical guidance. Always consult a healthcare provider before changing your diet significantly.
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Open calculator →FAQ
What is intermittent fasting?
Intermittent fasting (IF) is a dietary pattern that cycles between periods of fasting and eating. It does not specify which foods to eat, but when. Common protocols include 16:8, 18:6, 20:4, and OMAD. Research suggests IF may support weight management and metabolic health.
What is the 16:8 method?
The 16:8 method involves fasting for 16 hours and eating within an 8-hour window each day. For example: start eating at 12:00 PM, stop at 8:00 PM, then fast until 12:00 PM the next day. It is the most popular IF protocol because it naturally fits around sleep and is sustainable long-term.
Can I drink water during fasting?
Yes. Water, black coffee, plain tea, sparkling water, and other zero-calorie beverages do not break a fast. Adding sugar, milk, cream, or caloric supplements would break the fast. Stay hydrated — many people drink more water during fasting periods.
When does a fast break?
Any caloric intake breaks a fast. This includes food, fruit juice, milk, protein shakes, and caloric supplements. Black coffee, plain water, and plain tea are fine. Some argue that even small amounts of cream or sweeteners break a fast; strict adherents allow only plain water.