Seventy-two hours — three full days. This is serious extended fasting. Enter your start time and see exactly when it ends, then read the safety checklist below.
Your 72-hour fast ends —
Safety: 72-hour fasts are extended fasting: electrolytes + hydration daily, no hard training, stop at any concerning symptom. Not for pregnancy, eating disorders, or without a doctor's guidance if you have any medical condition or take medication.
The 72-hour checklist: electrolytes daily (sodium, potassium, magnesium), 2–3L water, no hard training, sleep protected. Most people find day two the hardest and day three strangely calm — but calm isn't a signal to extend.
Refeeding after 72 hours: small, light, low-fiber first meal; wait 1–2 hours; then eat normally. After three days, your digestive system needs a runway, not a landing strip.
Fluent Fast doesn't coach multi-day fasts beyond guidance — past 72 hours belongs with professional supervision. This calculator times your fast; your judgment (and ideally your doctor) runs it.
Healthy adults do them, but this length deserves real caution: electrolytes, hydration, no intense exercise, and an absolute stop at concerning symptoms. Medical conditions or medications mean talking to a doctor first — non-negotiable.
Mostly water and gut content plus some fat — much of the scale drop returns when you eat. Treat 72-hour fasts as a reset, not a weight-loss method.
Desk work, usually yes. Physical labor or hard training, no. Plan the fast around an easy stretch.
Save your schedule in Fluent Fast — free forever, no account needed.
Open in Fluent Fast →More calculators: 16:8 · 18:6 · 20:4 · OMAD · Fast end time · Eating window
Powered by Fluent Fast — the free fasting app that teaches you what's happening, celebrates your rhythm, and never charges you.