A free tool for planning your eating and fasting windows
The Intermittent Fasting Window Calculator makes fasting schedules simple. Intermittent fasting depends on timing, yet most people struggle to fit an eating window around their own wake time, bedtime and daily routine. This free tool turns your wake and sleep times into a clear eating window for the protocol you choose, with no spreadsheets, guesswork or sign-up.
You enter your wake time, your sleep time and a protocol: 14:10, 16:8, 18:6, 20:4 or OMAD (one meal a day). The calculator works backward from your bedtime so that your last meal ends a few hours before you sleep, and then shows:
Everything is calculated on your device. Nothing you enter is stored on our servers.
An eating window is only useful if you can keep to it. A schedule that makes you eat late at night, right before bed, is harder to sustain and may affect how well you sleep. Many people also find it easier to stick to a window that starts a little after waking and finishes a few hours before bedtime. The calculator takes that rhythm into account, so the schedule works with your day rather than against it. What suits you will still depend on your health, medication, work pattern and preferences.
The calculator applies simple arithmetic to the times you enter. The guidance in our articles draws on published research on time-restricted eating, circadian rhythm and sleep, and we link to the original sources where we cite them. Research on intermittent fasting is still developing and results vary from person to person, so we describe findings carefully and do not promise outcomes.
It does not give medical advice, and it does not account for medical conditions, medication, daylight-saving changes, time zones or your individual circadian rhythm. It cannot tell you whether fasting is right for you.
This tool is for information only and is not a substitute for professional medical advice. Intermittent fasting is not suitable for everyone. It is generally not recommended for pregnant or breastfeeding women, for children and teenagers, or for people with a history of eating disorders, and people with diabetes or other medical conditions, or who take medication, should speak to a healthcare provider first. Always consult a qualified professional before starting a new eating pattern, and stop and seek advice if you feel unwell. Please read our Terms of Service.
The calculator is free, with no account, no subscription and no supplements for sale. The site may display advertising and may contain affiliate links to related products or resources. If you buy through one we may earn a commission at no extra cost to you. Results are calculated from your times only and are never influenced by advertisers. See our Privacy Policy for how we handle data.
For longer explanations of fasting windows, autophagy timelines, eating schedules for shift work and common mistakes, read the guides on our blog.
Found a bug, have a feature suggestion, or noticed something in an article that needs correcting? Email aichajeral@gmail.com or use our contact page.