Fasting Timer

16:8 is the most popular starting point: you fast for 16 hours and eat within an 8-hour window. Once that feels easy, many people step up to 18:6 or 20:4. OMAD (one meal a day, a 23:1 split) is more advanced and is best tried after you are comfortable with longer fasts. This timer supports all of them plus a custom option.

Yes. The start time of your active fast is saved in your browser, so when you return the timer recomputes the remaining time from that stored timestamp. You can refresh, close the tab, or restart your device and the countdown picks up right where it left off.

Yes. Click "Enable notifications" before starting and grant the browser permission. When your fast finishes (and again when the eating window closes) the timer fires a notification if the tab is in the background. Notifications are optional and work without an account.

Yes - completely free with no sign-up. Your active fast and your log of recent fasts are stored locally in your browser, so nothing leaves your device and there is no account to create.

For most healthy adults, intermittent fasting is safe. Common short-term effects include hunger, fatigue, and irritability as your body adjusts, which usually ease within a week or two. Fasting is not recommended for people who are pregnant or breastfeeding, have a history of eating disorders, have diabetes or blood sugar issues, or take medications that require food. If you have any medical condition or take medication, check with your doctor before starting.

Start with 14:10 (a 14-hour fast, 10-hour eating window) using the custom option for a week or two, then step up to 16:8 once it feels comfortable. 14:10 is gentler because the eating window is larger, so it is easier to fit in your meals and less likely to leave you hungry. Jumping straight to 16:8 or longer can work, but easing in tends to be more sustainable.

Fasting can help with weight loss, but only because it tends to make you eat fewer calories overall - the fast itself has no magic fat-burning effect. By restricting your eating window, many people naturally consume less. Weight loss still comes down to a calorie deficit, so what you eat during the eating window matters. Track your intake with our calories remaining calculator to make sure the deficit is there.

Water, black coffee, and plain tea are generally considered fine during a fast because they contain negligible calories and will not meaningfully break the fast. Avoid anything with calories, sugar, or milk, including juice, bone broth, and most milky drinks. Staying hydrated actually makes fasting easier and helps reduce hunger pangs.