Intermittent Fasting Window Calculator
Calculate your fasting and eating windows based on your chosen IF protocol and preferred eating start time.
Formulas Used
Eating window end time:
Eating End = Eating Start + Eating Hours
Fasting window:
Fasting Start = Eating End
Fasting End = Eating Start (next day)
Eating Hours = 24 − Fasting Hours
Estimated TDEE (sedentary baseline):
TDEE ≈ Body Weight (kg) × 30 kcal/kg/day
Fat-loss calorie target:
Target = TDEE × 0.80 (20% deficit)
Autophagy onset (time-restricted eating):
Autophagy Start ≈ Fasting Start + 16 hours
5:2 weekly calorie deficit:
Weekly Deficit = 2 × (TDEE − Fasting Day Calories)
Est. Fat Loss (kg/week) = Weekly Deficit ÷ 7,700
Assumptions & References
- Autophagy (cellular self-cleaning) is estimated to begin after ~16 hours of fasting (Alirezaei et al., 2010, Autophagy).
- Early time-restricted eating (eTRE, e.g., 8 AM–4 PM) shows superior metabolic outcomes vs. late windows (Sutton et al., 2018, Cell Metabolism; Wilkinson et al., 2020, Cell Metabolism).