Intermittent Fasting Calculator
Track your fasting windows, calculate eating periods, and monitor your intermittent fasting progress.
Fasting Settings
kcal
Current Zone
Fat Burning
12.0 hours fasted
Fasting Progress75%
4.0 hours until eating window (12:00)
🕐Fasting Window
16h
🍽️Eating Window
8h
🥗Meals in Window
2
🔥Cal/Meal
1000
During Your Fast
- • Water, black coffee, and plain tea are OK
- • Avoid any calories to maintain fast
- • Stay hydrated - aim for 8+ glasses of water
- • Light activity is fine, avoid intense exercise
Fasting Zones Timeline
| Hours | Zone | What Happens |
|---|---|---|
| 0-4h | Fed State | Body digests and absorbs food, insulin rises |
| 4-12h | Early Fasting | Insulin drops, body starts using stored glucose |
| 12-18h | Fat Burning | Glycogen depletes, body switches to burning fat |
| 18-24h | Ketosis | Ketone production increases, enhanced fat burning |
| 24h+ | Autophagy | Cellular cleanup and regeneration begins |