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Health
Intermittent Fasting Calculator
Calculate your intermittent fasting eating window for 16:8, 18:6, OMAD, 20:4, 5:2 and more. Live countdown timer, fasting benefit stages, and workout tips. Free IF calculator.
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⏱ Fasting Protocol
🕐 Schedule Settings
🕐 24-Hour Schedule
Hover over a segment for details
Eating (8h)
Fasting (16h)
Now
⏳ Currently: Fasting
1h 29m
until eating window opens at 12:00
Ketosis Entry — Blood ketones rising, fat burning accelerated, mental clarity.
📅 Daily Schedule
🟢 Start eating
12:00
Break your fast with protein + fat
🔴 Stop eating
20:00
Begin your fasting window
⚗️ Autophagy
08:00
~12h into fast — cellular cleanup starts
🔥 Deep autophagy
12:00
16h — peak repair & fat burn
🏋️ Workout Timing Advice
Training fed (11:00)
• ✅ Optimal strength and performance
• ✅ Better muscle protein synthesis post-workout
• 💡 Eat 1–2h before training, refuel within 1h after
📈 Fasting Benefits Timeline
0h
Fed State
Insulin high, body burning glucose from food.
4h
Post-absorptive
Digestion complete, insulin dropping, fat burning begins.
8h
Lipolysis
Liver glycogen depleting, body increasingly using fat.
12h
Early Autophagy
Cellular cleanup begins. Growth hormone starts rising.
14h
Ketosis Entry
Blood ketones rising, fat burning accelerated, mental clarity.
16h
Deep Autophagy
Peak cellular repair and regeneration. Insulin at lowest.
💡 16:8 Tips
→Skip breakfast — start your eating window at noon if you go to bed at midnight.
→Black coffee, plain tea, and water are fine during your fast.
→For workouts: train 1–2h before your first meal for optimal fat burn.
→Break your fast with protein + fat first to avoid an insulin spike.
→Electrolytes (sodium, magnesium) reduce fasting hunger and headaches.
📆 Weekly View
Mon
12:00
20:00
Tue
12:00
20:00
Wed
12:00
20:00
Thu
12:00
20:00
Fri
12:00
20:00
Sat
12:00
20:00
Sun
12:00
20:00
💡 Consistency is more important than perfection. Same eating window every day = better results.
Frequently Asked Questions
What is the 16:8 intermittent fasting schedule?+
You fast for 16 hours and eat within an 8-hour window. For example, eating from 12pm to 8pm and fasting from 8pm to 12pm the next day.
When does autophagy start during fasting?+
Autophagy (cellular cleanup) begins around 12–14 hours into a fast and peaks around 16–18 hours. This is one of the key health benefits of extended fasting.
Is it better to work out fasted or fed?+
Fasted training increases fat oxidation but may reduce strength output by ~5%. Training 1-2h before your first meal is a popular middle-ground strategy.