Fasting Protocol
Your total daily calorie intake during eating days. Calorie needs vary by body size, activity, and goals.
Fasting Schedule
Select a protocol and click generate.
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What This Calculator Does
This intermittent fasting schedule calculator generates a personalized eating and fasting window based on your chosen IF protocol, first meal time, and daily calorie target. It supports the most popular protocols: 12:12 (beginner), 14:10, 16:8 (most popular), 18:6, 20:4 (Warrior Diet), OMAD (one meal a day, 23:1), and 5:2 (two low-calorie days per week). The calculator distributes your daily calories across the meals in your eating window.
The Formula
Intermittent fasting restricts when you eat rather than what you eat. The 16:8 protocol means fasting for 16 hours and eating within an 8-hour window. For example, if your first meal is at noon, your eating window closes at 8 PM and fasting resumes until noon the next day. The 5:2 protocol is different: you eat normally five days per week and restrict calories to approximately 25% of normal on two non-consecutive days.
Step-by-Step Example
Choose a protocol
16:8 Standard selected. This is the most researched and popular IF protocol.
Set first meal time
First meal at 12:00 PM. Eating window: 12:00 PM to 8:00 PM. Fasting window: 8:00 PM to 12:00 PM.
Enter calorie target
Daily calories: 2,000. Three meals in the eating window.
Review schedule
Each meal: approximately 667 calories. Water, black coffee, and unsweetened tea are allowed during the fasting window.
Real-World Use Cases
Weight Management
IF naturally reduces calorie intake by limiting the eating window. Research shows 16:8 participants typically consume 200 to 500 fewer calories per day without counting.
Metabolic Health
Time-restricted eating has been shown to improve insulin sensitivity, reduce fasting glucose, and lower blood pressure in multiple 2024-2026 clinical trials.
Simplified Meal Planning
Fewer meals means less time cooking and cleaning, reduced decision fatigue around food, and easier calorie tracking.
Common Mistakes to Avoid
Starting with an aggressive protocol. Jumping directly to 20:4 or OMAD without adaptation often leads to binge eating during the eating window. Start with 12:12 and gradually extend.
Overeating during the eating window. IF is not a license to eat unlimited calories. You still need a calorie deficit for weight loss and balanced nutrition for health.
Drinking caloric beverages during the fast. Juice, milk, sweetened coffee, and sports drinks break your fast. Stick to water, black coffee, and plain tea.
Ignoring hunger cues and pushing through extreme discomfort. Mild hunger is normal when starting IF, but persistent dizziness, weakness, or inability to concentrate means you should eat.
Frequently Asked Questions
Accuracy and Disclaimer
Intermittent fasting is not appropriate for everyone. It is contraindicated for pregnant or breastfeeding women, children, individuals with a history of eating disorders, and people with certain medical conditions (diabetes, low blood pressure, underweight). Consult a healthcare provider before starting any fasting protocol.
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