⏰ Intermittent Fasting Calculator
Intermittent fasting works by compressing all eating into a daily window — 16:8 is the most popular, meaning 16 hours fasting and 8 hours eating. The tricky part is translating the protocol into actual clock times around your schedule.
Pick your protocol, enter when you finished your last meal, and this calculator shows exactly when your fast ends and your eating window closes, so there is never any guesswork.
How to use this calculator
Choose a fasting protocol, enter the time of your last meal, and get your precise fasting-end and eating-window times.
- Select your protocol (16:8, 18:6, 20:4 or OMAD).
- Enter the time you finished your last meal.
- Follow the shown fasting-end and eating-window times.
What Is the Best Intermittent Fasting Schedule?
For beginners, 16:8 is the sweet spot: finish dinner at 8 PM, skip breakfast, eat between noon and 8 PM. It is sustainable because most of the fast happens while you sleep. Once adapted, many move to 18:6 for faster fat loss, and experienced fasters try OMAD (one meal a day) a few times per week. Consistency beats intensity — a 16:8 you follow daily outperforms a 20:4 you quit in a week. Black coffee, tea and water are fine during the fast; anything with calories breaks it.
Frequently asked questions
What can I drink during intermittent fasting?
Water, black coffee and plain tea are fine — zero calories. Avoid anything with calories, including bulletproof coffee, juice and diet sodas with sweeteners that spike insulin.
Will intermittent fasting slow my metabolism?
Short daily fasts do not meaningfully slow metabolism; some studies show a slight increase in norepinephrine. Prolonged multi-day fasts are a different story — stick to daily windows.
Can I exercise while fasting?
Yes — many people train fasted with good results. Keep intensity moderate at first, hydrate well, and schedule your eating window after workouts when possible.
How long until I see results from 16:8?
Most notice less bloating within a week and measurable fat loss in 3-4 weeks, assuming the eating window is not a free-for-all. Track waist measurements, not just scale weight.
Is OMAD safe every day?
OMAD suits some experienced fasters but is hard to sustain daily and risks nutrient gaps. Most do better with 16:8 or 18:6 daily and OMAD occasionally.