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Free FastingCalculator

When can I eat?

The question every faster asks. Enter your last meal time and how long you're fasting: this fasting time calculator answers instantly, with your full eating window and a 24-hour timeline.

Fasting duration

How to calculate your fasting time

Your fast ends exactly your chosen number of hours after your last meal:last meal + fasting hours = eating time. That one line is the entire secret behind every fasting time calculator on the internet. The part people get wrong is the calendar: most fasts cross midnight, so "8:15 PM plus 16 hours" means 12:15 PMtomorrow, and a fast started after midnight ends the same day. This calculator handles the date change and labels the answer "today" or "tomorrow" so there's no ambiguity, and it works for any duration, from a 12-hour overnight fast to a multi-day custom fast.

If you searched "how to find your fasting time" or "how do I figure out my fasting time", this is the whole method. You don't need an app, an account, or a quiz about your age and weight; those don't change the arithmetic. You need two numbers and a tool that handles midnight correctly.

Quick reference from an 8 PM last meal

Fast lengthYou can eat atMatching protocol
12 hours8:00 AM next day12:12
14 hours10:00 AM next day14:10
16 hours12:00 PM next day16:8
18 hours2:00 PM next day18:6
20 hours4:00 PM next day20:4
23 hours7:00 PM next dayOMAD
36 hours8:00 AM, two days onExtended (custom)

Ate at a different time? Use the calculator above; it works with any last-meal time and any duration, then lets you start a timer, share the schedule, print it, or add it to your calendar.

From answer to action

Knowing your eating time is step one; remembering it at hour thirteen is the real problem. That's why every result here connects to the rest of the toolkit. "Start fast" launches alive fasting timerthat counts down to the exact minute, survives closed tabs, and rolls into your eating window when the fast completes. "Add to calendar" generates events for your fast end and window close. And every completed fast lands in yourlocal history, so over a few weeks you can see your actual average fasting time, which is far more useful than any single day's answer.

Common timing mistakes

  • Counting from bedtime instead of the last bite. The fast starts when eating stops. A 9:30 PM snack after an 8 PM dinner moves your entire window 90 minutes later.
  • Rounding across midnight. "About 16 hours from 8-ish" drifts surprisingly far. Exact times keep your tracking honest, and the calculator makes exact effortless.
  • Confusing fast length with wake-up time. Your fast ends a fixed number of hours after your last meal, not at a fixed clock time. Eat later, and the end moves later with it, unless you deliberately switch to a fixed eating window, which is what theschedule planner builds.
  • Treating a shifted fast as a failed fast. If dinner ran late, the honest response is a later end time, not abandoning the day. Our timer's "Edit start time" exists precisely for this.

Common questions

When can I eat after a 16 hour fast?

Add 16 hours to your last meal. If you finished eating at 8:15 PM, you can eat at 12:15 PM the next day. Enter your own times above for an exact answer with your full eating window and a Start Fast button.

How do I find my fasting time?

Your fasting time is defined by two numbers: when your last meal ended and how many hours you plan to fast. Add them together and you have your eating time. This calculator does it instantly, handles the midnight crossing, and tells you whether the answer lands today or tomorrow: no mental arithmetic, no app download, and completely free.

How do I know my fasting time for free?

Right here: this fasting time calculator is free with no account, no trial, and no payment. Some apps put this basic answer behind a signup or subscription; the calculation is simple arithmetic and should never cost anything.

When does my fast end if I started at 8 PM?

It depends on your fasting duration: a 12-hour fast ends at 8 AM, 14 hours at 10 AM, 16 hours at 12 PM, 18 hours at 2 PM, and 20 hours at 4 PM the next day. A 24-hour fast ends at 8 PM the following evening.

Does drinking water break a fast?

Plain water is generally considered compatible with fasting, and most protocols also allow black coffee and unsweetened tea. Anything with meaningful calories ends the fast for scheduling purposes. There is no single official rule; pick a definition and apply it consistently so your tracking is comparable day to day.

What should I eat when my fast ends?

That is a nutrition question this scheduling tool deliberately stays out of: we calculate when your window opens, not what belongs in it. General guidance about breaking fasts is best sourced from qualified nutrition professionals, especially for longer fasts.

What if I ate later than planned?

Recalculate from your actual last meal: the fast simply shifts. If you use our timer, press "Edit start time" and it recalculates without treating the change as a failure. Your history records the actual times, not the intended ones.

Can I set a reminder for when I can eat?

Yes, two ways: press "Start fast" to run the live countdown timer, or press "Add to calendar" to download a calendar file with your fast end and eating window as events, generated locally with no calendar account access needed.

Is there a free app that tells me when I can eat?

This page is that tool, minus the install: it answers in one tap in any browser, free, and the timer keeps answering live for the rest of the fast. Many app-store timers charge subscriptions for exactly this arithmetic; the calculation has never been worth paying for.

When can I eat after an 18 or 20 hour fast?

Same method, bigger number: an 8 PM last meal means eating at 2 PM next day after 18 hours, or 4 PM after 20. Select 18:6 or 20:4 above, or any custom duration, and the calculator gives your exact time with the correct day label.