⚡ Quick Answer

Intermittent fasting (IF) cycles between eating and fasting periods. Most popular: 16:8 (fast 16 hours, eat in 8-hour window). If you stop eating at 8 PM and skip breakfast until noon: that is 16 hours fasting! Your eating window is 12 PM - 8 PM. Fasting promotes fat burning, insulin sensitivity, and cellular repair (autophagy).

📂 Health

⏰ Intermittent Fasting Calculator

Calculate your intermittent fasting schedule. Find your eating window, fasting start and end times, and when your body enters ketosis. Track your IF schedule easily!

✏️ Enter Your Values

🍽️ Last meal time (when you STOP eating) ⏰ Fasting Protocol 📅 Days per week you plan to fast

✨ Your Result

🦉Owl's Explanation

⏰

Fill in the values above and click Calculate ✨

✅ Trusted Tool

The 365tool.net Intermittent Fasting Calculator helps plan your fasting schedule. Results are for planning purposes only. Consult a healthcare professional before starting any fasting protocol if you have medical conditions. No sign-up needed.

🤔 How Does This Work?

The Intermittent Fasting Calculator finds your daily schedule:

Takes your last meal time and fasting duration
Calculates when your fast starts (last meal time)
Adds fasting hours to find when you break the fast (first meal)
Shows your eating window end time (same as fast start)
Indicates when key metabolic transitions occur (glycogen depletion ~12h, ketosis ~16-24h)

❓ Frequently Asked Questions

What is intermittent fasting?▼

Intermittent fasting (IF) is an eating pattern that cycles between periods of fasting and eating. It does not specify which foods to eat — only when. During fasting, you drink water, black coffee, or plain tea. After 12-16 hours of fasting, your body depletes glycogen and begins burning fat.

What are the benefits of intermittent fasting?▼

Research-supported benefits: weight loss and fat burning (especially visceral/belly fat), improved insulin sensitivity, reduced inflammation, cellular autophagy (cellular clean-up), possible longevity benefits, improved mental clarity in the fasted state, simplifies eating (fewer meals to prepare). Results vary by individual.

Can I drink coffee during fasting?▼

Black coffee (no milk, cream, or sugar): yes, does not break the fast and may enhance fat burning. Plain water and herbal tea: yes. Anything with calories technically breaks the fast. Some experts allow very small amounts of fat (MCT oil, butter) while others say any calorie breaks the fast. For beginners, stick to black coffee and water.

Is intermittent fasting safe?▼

Generally safe for healthy adults. Not recommended for: pregnant or breastfeeding women, people with eating disorder history, people with diabetes on medication (can cause dangerous blood sugar drops), those who are underweight, children. Consult a doctor before starting if you have any medical conditions.

What should I eat in my eating window?▼

IF works best when combined with healthy food choices. Focus on whole foods: lean proteins, vegetables, fruits, whole grains, healthy fats. Avoid: processed foods, excess sugar, refined carbohydrates. The eating window does not mean you can eat unlimited unhealthy food — caloric intake and food quality still matter.