Fasting Window End Time Calculator
Enter when your fast started and how long it runs to see exactly when it ends and your eating window opens and closes.
How it works
fast ends = start time + fasting hours · eating window = 24 − fasting hours (for fasts under a day) · window closes = fast-end + eating-window hours
Time-restricted eating splits a 24-hour day into a fasting block and an eating window, so once you fix the start and the fasting length the end time is just addition. A 16:8 pattern fasts for 16 hours and eats within the remaining 8. Fasts that start in the evening usually end the following day, which the calculator marks. For fasts of a full day or longer there is no recurring daily window, so only the end time is shown.
Worked example
A 16-hour fast begun at 20:00 (8 PM) ends at 12:00 noon the next day, opening an 8-hour eating window that closes at 20:00 — the classic 16:8 schedule.
Frequently asked questions
When does my fast actually start?
Count from the end of your last meal or calorie-containing drink, not from bedtime. Black coffee, plain tea and water generally do not break a fast, but anything with calories does.
What does 16:8 mean?
It is 16 hours fasting followed by an 8-hour eating window each day. Enter 16 as the fasting length and the calculator shows the 8-hour window automatically.
Can I do longer fasts like 18:6 or 20:4?
Yes — enter 18 or 20 hours and the eating window shrinks to 6 or 4 hours accordingly. Fasts of 24 hours or more (like eat-stop-eat) have no daily window, so only the end time is given.
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Educational only — not medical or nutritional advice. Consult a professional before starting a fasting routine.