See exactly when to eat and fast. This free intermittent fasting timer turns methods like 16:8 into clock times for your eating and fasting windows — a simple timing helper, no calorie or weight targets.
Pick when you’d like to start eating each day. The timer shows your eating and fasting windows as clock times. Choose a pattern that fits your life and feels comfortable.
A simple timing helper, not medical or nutrition advice. Intermittent fasting isn’t right for everyone — if you’re pregnant, have diabetes, an eating-disorder history or a health condition, check with a doctor first. Drink water and don’t push through feeling unwell.
How the Intermittent Fasting Window Timer Works
This tool turns a fasting method and a start time into two clock-time windows: when you eat and when you fast. It doesn’t touch calories or weight — it’s purely a scheduling helper that does the time math for you.
Formula: Eating hours = 24 − Fasting hours (F). Eating window end = Start time + Eating hours. Fasting window runs from the eating window end back around to the next day’s Start time, and lasts F hours.
- Method — the fasting pattern you pick (16:8, 14:10, 18:6, or 20:4), which sets F, the number of fasting hours
- Start time — the clock time you’d like your eating window to begin each day
- Eating hours — 24 minus F, i.e. how many hours you can eat in
- Eating window — the clock-time range from your start time to start time + eating hours
- Fasting window — the remaining F hours, from the end of the eating window until your start time comes around again
Example Scenarios
| Method | Eating Window Starts | Eating Window Ends |
|---|---|---|
| 16:8 | 12:00 PM | 8:00 PM |
| 14:10 | 8:00 AM | 6:00 PM |
| 18:6 | 1:00 PM | 7:00 PM |
| 20:4 | 11:00 AM | 3:00 PM |
| 16:8 | 9:00 AM | 5:00 PM |
| 14:10 | 7:30 AM | 5:30 PM |
Intermittent Fasting Window Timer FAQ
What does “16:8” mean in intermittent fasting?
It means a 16-hour fasting window paired with an 8-hour eating window each day. The first number is hours fasted, the second is hours you’re free to eat, and together they always add up to 24.How do I pick a start time for my eating window?
Pick a time that fits your routine, such as right after you’d normally eat breakfast or lunch. There’s no single correct start time — the timer just converts your chosen method and start time into clock hours so you can plan around it.Can I change my eating window start time from day to day?
Yes. The timer recalculates instantly whenever you change the start time or method, so you can check a new schedule any time your day shifts, like on weekends versus workdays.What’s the difference between 18:6 and 20:4?
18:6 gives you a 6-hour eating window and 18 hours fasting; 20:4 narrows that to a 4-hour eating window with 20 hours fasting. Shorter eating windows are generally considered a more advanced step up from 16:8.Is intermittent fasting safe for everyone?
No. This is a scheduling helper, not medical advice. Fasting isn’t appropriate for everyone — people who are pregnant, have diabetes, have a history of an eating disorder, or have another health condition should check with a doctor before trying it.Does the timer account for time zones or daylight saving time?
No, it works purely off the clock time you enter and does not adjust for time zone changes or daylight saving transitions. If your schedule shifts across one of those, just re-enter your intended start time.Related Calculators
If you’re exploring fasting more broadly, the water fasting safety guide covers a stricter approach and its risks, while the intermittent fasting calculator connects your schedule to calorie targets. You can also check your total daily energy expenditure (TDEE) to see how your eating window fits your overall calorie needs.