What time should I stop eating on 16:8?

On a 16:8 schedule with an 8-hour eating window, stop eating 8 hours after your first meal. For example, if you start eating at noon, stop by 8:00 PM, then fast for 16 hours until noon the next day.

Does the calculator work for 18:6, 20:4 and OMAD?

Yes. Choose any protocol and the calculator adjusts the eating window automatically — 6 hours for 18:6, 4 hours for 20:4, and about 1 hour for OMAD (23:1).

Can I start the timer from the calculator?

Yes. After you set your schedule, tap Start this fast to open the live timer with your protocol already selected.

Fasting window calculator

To eat at noon on a 16:8 schedule, stop eating by 8:00 PM the day before — an 8-hour eating window and a 16-hour fast.

Fasting protocol

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Your plan

16:8: eat from 12:00 PM to 8:00 PM. Then fast from 8:00 PM to 12:00 PM next day.

Eating window12:00 PM – 8:00 PM

Fasting window8:00 PM – 12:00 PM (next day)

16h fast · 8h eating window

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See the 16:8 protocol Check what breaks a fast

Fit a schedule to your day

Add your wake, sleep, and meal times to get a few practical fasting windows.

Routine planning only, not medical advice.

Wake time

Bedtime

Preferred first meal

Preferred last meal

Workout time (optional)

Suggested windows

16:8
Eating window: 12:00 PM – 8:00 PM
Fasting window: 8:00 PM – 12:00 PM (next day)
Matches your meal times
14:10
Eating window: 11:00 AM – 9:00 PM
Fasting window: 9:00 PM – 11:00 AM (next day)
Close to your meal times
18:6
Eating window: 1:00 PM – 7:00 PM
Fasting window: 7:00 PM – 1:00 PM (next day)
Close to your meal times

Work out exactly when to stop eating and when your eating window opens for any fasting schedule.

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Frequently asked questions

What time should I stop eating on 16:8?: On a 16:8 schedule with an 8-hour eating window, stop eating 8 hours after your first meal. For example, if you start eating at noon, stop by 8:00 PM, then fast for 16 hours until noon the next day.
Does the calculator work for 18:6, 20:4 and OMAD?: Yes. Choose any protocol and the calculator adjusts the eating window automatically — 6 hours for 18:6, 4 hours for 20:4, and about 1 hour for OMAD (23:1).
Can I start the timer from the calculator?: Yes. After you set your schedule, tap Start this fast to open the live timer with your protocol already selected.

FastWindowTimer provides general information and planning estimates, not medical advice. Fasting isn't right for everyone — if you are pregnant, have a history of an eating disorder, have diabetes, or take medication, talk to a clinician first.