Intermittent Fasting Window Calculator
Place a user-chosen fasting and eating window on the clock with daily local reminders, without recommending a regimen or benefit. Sensitive inputs stay in your browser.
CalcSpan can place a schedule on a clock, but it does not select a fasting regimen for you.
Context matters.
- People with health conditions, pregnancy, a history of eating disorders or medication timing needs should seek appropriate professional guidance before fasting.
Sources & scope
The calculation guide and this source trail show what the result means, where the rule came from and when it was last reviewed. This is source-and-calculation QA, not a claim of medical, legal, tax or other professional review; time-sensitive decisions still belong with the linked authority.
A visible path from input to answer.
Place a user-chosen fasting and eating window on the clock with daily local reminders, without recommending a regimen or benefit. The page keeps the calculation scope and its limits beside the result so the output can be checked, copied or revisited.
- Read the record. The calculator uses Schedule starts, Fasting starts, Fasting window (hours) and Eating window (hours) and 1 additional field supplied in the form.
- Apply the scope. It applies the User-chosen time-window scheduling only — no regimen, benefit or weight-loss recommendation reference and the explicit date, unit and counting conventions shown in the result.
- Expose the checkpoints. Intermediate rows, warnings and timeline events stay visible; the emphasized row identifies the primary checkpoint when one exists.
CalcSpan can place a schedule on a clock, but it does not select a fasting regimen for you.
- ConfirmationNot yet confirmed
Calculation purpose: Place a user-chosen fasting and eating window on the clock with daily local reminders, without recommending a regimen or benefit. This is a high-sensitivity reference output; the linked authority or qualified professional controls the final decision.
Calendar inputs use plain year-month-day semantics. Leap days, month ends, date-pair order and unsupported dates are checked before the result is shown.
Rule set 1.1.0 · Last reviewed 2026-08-23 · Next review due 2027-02-23. The source panel below contains the linked evidence.
What to know before using the result.
When does a 16:8 fasting window end?
A 16-hour window ends 16 hours after the entered start; the following eight-hour eating window is shown on the local clock.
Does CalcSpan recommend intermittent fasting?
No. It only schedules a regimen the user has already chosen or confirmed and makes no benefit or weight-loss claim.
Can I save a daily fasting reminder?
Yes. A confirmed result can be saved locally in My Spans or added to a calendar without uploading the entered schedule.