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Intermittent Fasting Calculator
Pick your fasting method and first meal to see your eating window.
Eating window
—
When to eat.
| Fast for | — |
|---|---|
| Eat for | — |
| Window ends | — |
| Fast until | — |
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Enter your figures above to see the step-by-step working.
Everything computed client-sideEverything computed client-side — nothing leaves this page
How the Intermittent Fasting Calculator Works
Intermittent fasting splits the day into a fasting window and an eating window. The popular 16:8 method fasts for 16 hours and eats within an 8-hour window; 18:6, 20:4 and OMAD (one meal a day, ~23-hour fast) are stricter versions. Tell the calculator your method and when you plan to have your first meal, and it works out when your eating window closes and how long you’ll fast.
The eating window is simply 24 hours minus the fasting hours, starting at your first meal. Nothing about the food changes — only the timing.
eating window = first meal to first meal + (24 − fast hours)
Frequently Asked Questions
What is 16:8 intermittent fasting?
You fast for 16 hours and eat all your food within an 8-hour window — for example, noon to 8 pm.
When should I have my first meal?
Whenever suits you; the window just runs from there. This calculator shows exactly when it closes and when the fast resumes.
Does OMAD mean one meal a day?
Yes — a roughly 23-hour fast with a single one-hour eating window.
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