Intermittent Fasting Calculator
Determine your optimal fasting and eating windows based on your schedule and preferred fasting method
Calculate Your Fasting Schedule
Select Fasting Protocol
16:8 Method
16 hours fasting, 8 hours eating window
Most popular & beginner-friendly
18:6 Method
18 hours fasting, 6 hours eating window
Intermediate level
20:4 Method (Warrior Diet)
20 hours fasting, 4 hours eating window
Advanced level
OMAD (One Meal A Day)
23 hours fasting, 1 hour eating window
Expert level
5:2 Diet
5 days normal eating, 2 days restricted calories
Weekly schedule
Alternate Day Fasting
Alternate between fasting days and eating days
Most challenging
Your Schedule Preferences
When you want to start your eating window
Understanding Intermittent Fasting Methods
| Method | Description | Suitable For | Difficulty |
|---|---|---|---|
| 16:8 | Fast for 16 hours, eat during an 8-hour window | Beginners, most people | Low |
| 18:6 | Fast for 18 hours, eat during a 6-hour window | Those adapted to 16:8 | Medium |
| 20:4 (Warrior) | Fast for 20 hours, eat during a 4-hour window | Experienced fasters | High |
| OMAD | One meal a day, typically a 23:1 schedule | Advanced practitioners | Very High |
| 5:2 Diet | Eat normally 5 days, restrict calories (~500-600) for 2 days | Those who prefer weekly cycles | Medium |
| Alternate Day | Alternate between fasting days and regular eating days | Those seeking maximum results | Very High |
Most people start with the 16:8 method as it's the most sustainable for beginners. You can gradually extend your fasting window as your body adapts.
Health Benefits of Intermittent Fasting
-
Weight Loss: Reduces calorie intake and increases fat burning by improving hormone function.
-
Insulin Sensitivity: Can dramatically lower insulin levels, making stored body fat more accessible.
-
Cellular Repair: Induces autophagy, the process where cells remove damaged components.
-
Brain Health: May increase BDNF hormone levels and may aid the growth of new nerve cells.
-
Inflammation Reduction: Studies show a reduction in markers of inflammation, a key driver of many diseases.
-
Heart Health: May improve various risk factors for heart disease, including blood pressure and cholesterol levels.
Common Questions
Can I drink during fasting?
Water, black coffee, tea without milk/sugar, and zero-calorie beverages are generally acceptable during fasting periods.
Will I lose muscle?
When combined with resistance training and adequate protein intake during eating windows, intermittent fasting can preserve muscle mass.
Who should NOT fast?
People who are underweight, pregnant or breastfeeding, under 18, or have certain medical conditions should not practice intermittent fasting without medical supervision.
Will fasting slow my metabolism?
Short-term fasting periods (like those in IF protocols) have not been shown to significantly slow metabolism, especially when compared to continuous calorie restriction.
How long until I see results?
Many people notice initial changes in 2-4 weeks, with more significant benefits coming after 8-12 weeks of consistent practice.
Implementation Strategies for Success
Getting Started
- Start with a more modest fasting window (like 12:12) and gradually extend it
- Try to align your eating window with your most active hours of the day
- Stay well-hydrated during fasting periods to help manage hunger
- Keep busy to distract yourself from hunger during initial adjustment
- Track your fasting hours using the timer or a mobile app
Maintaining Your Fast
- Focus on nutrient-dense foods during your eating window
- Don't compensate for fasting by overeating during your eating window
- Allow for flexibility in your schedule for social events
- Consider timing workouts toward the end of your fasting period
- Listen to your body - if you feel unwell, break your fast