Intermittent Fasting Calculator
Pick an intermittent fasting protocol and start time to see your eating and fasting windows in clock time on a simple 24-hour timeline.
Updated August 3, 2026
Medical Disclaimer: This tool provides general estimates for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, exercise, or health routine. Read our full Medical Disclaimer.
How This Is Calculated
This is a scheduling tool, not a physiological calculator. Your eating and fasting windows come from the protocol you choose, not from your personal stats.
Step 1: Choose Your Protocol
16:8, 18:6, and 14:10 are daily protocols defined by the number of fasting hours to eating hours. 5:2 and alternate-day fasting instead work on a day-based weekly pattern rather than a daily clock-time window.
Step 2: Set Your Eating Window Start Time
For daily protocols, we take your chosen start time and the protocol’s eating-hour count to calculate your exact eating and fasting windows in clock time.
Step 3: Display the Result as a Timeline
Rather than plain text alone, we show your eating and fasting windows as a color-coded 24-hour timeline bar, making your schedule easy to read and share at a glance.
A Note on Accuracy
This is a scheduling tool, not a physiological calculator — your window length is a protocol choice, not something derived from your personal stats. Research to date generally shows intermittent fasting produces weight loss comparable to standard calorie restriction, not a distinct metabolic advantage. Intermittent fasting is not appropriate for everyone: people with a history of disordered eating, pregnant or breastfeeding people, and those with certain medical conditions (such as insulin-dependent diabetes) should consult a doctor before trying it.
Frequently Asked Questions
Does Intermittent Fasting Burn More Fat Than Regular Calorie Restriction?
Research to date generally shows intermittent fasting produces weight loss comparable to standard calorie restriction with the same calorie deficit — not a distinct metabolic advantage. Its main benefit for many people is that a shorter eating window can make it easier to stick to a calorie target.
Which Protocol Should I Choose?
There's no single best protocol — it depends on what fits your schedule and lifestyle. 16:8 and 14:10 are common starting points with a daily eating window, while 5:2 and alternate-day fasting work on a weekly, day-based pattern instead.
Is Intermittent Fasting Safe for Everyone?
No. People with a history of disordered eating, pregnant or breastfeeding people, and those with certain medical conditions (such as insulin-dependent diabetes) should consult a doctor before trying intermittent fasting.
How Do 5:2 and Alternate-Day Fasting Work Differently From 16:8?
16:8, 18:6, and 14:10 are daily eating-window protocols — you eat and fast at the same times every day. 5:2 involves eating normally 5 days a week and significantly restricting calories on 2 non-consecutive days. Alternate-day fasting alternates between normal eating days and fasting or very-low-calorie days.
Sources
Clinical application of intermittent fasting for weight loss: progress and future directions — Varady et al. (2021), Nature Reviews Endocrinology, 18, 309–321