Free 16:8 Intermittent Fasting Timer App for Android

Day Organizer & Disciplinizer For 2 Meals a Day Eaters

Not just one of many apps - it will become an inseparable part of your life!

The timer is still under construction and not published. If you want to be notified when it is available for download, please send an email with the subject "IntFastApp" (and an empty body) to

The current stage of the app development cycle:

* Design.
* Main development.
* Alpha testing (by the developer).
* Beta testing (by voluntary users - send an email with the subject "IntFastAppBeta" to if you want to be one of them).
* Publishing in the Play Store.

This app supports the 16:8 protocol of Intermittent Fasting:

That picture illustrates the first 4 rules described in HOW TO START: A CRASH COURSE (that link is also accessible through the app's menu).

This page describes the app's functionality in detail, however, you don't need to read it. Instead, just start using the app and it will instruct you on what to do (and what not to do!) at each stage of the 16:8 cycle.

The app is very simple - it has only one button! The text in the button changes throughout the day, showing "START MEAL 1", "FINISH MEAL 1", "START MEAL 2" or "FINISH MEAL 2". You only need to abide by one important rule - the Traffic Lights Rule:

You can eat only when the timers are in green color.

If the timers are red, eating is prohibited until they turn green.

The app is customizable. In the Settings screen, you can pre-program the following 3 time periods (which correspond to the first 3 rules):

  • Maximum EATING WINDOW (4, 5, 6, 7 or 8 hours). So, the protocols 20:4, 19:5, 18:6 and 17:5 are supported as well.
  • Maximum meal duration (15, 20, 25, 30, 35 or 40 minutes).
  • Minimum gap between meals (3, 4 or 5 hours).
These settings are taken into account by the informative messages which help you to plan your day. For example, when you are in between meals or fasting, the app says how much time you have to wait until the next meal, and displays the EARLIEST time when you can start it. In between the meals, it also displays the LATEST time when you can start MEAL 2 and still stay in the EATING WINDOW.

Now you are ready to use the app. If you want even more details, keep reading.

The full 16:8 cycle consists of 4 time periods:

  • "MEAL 1"
  • "AFTER MEAL 1" (i.e. the gap between the meals)
  • "MEAL 2"
Obviously, the last 3 periods make up the "EATING WINDOW".

The upper timer counts the duration of the meals, and of the gap between them. Shown only during the EATING WINDOW.

The lower timer counts the duration of the current WINDOW (be it FASTING or EATING).


When opening the app before your 1st meal, you're shown how much time you have been fasting for (if still red - keep fasting!):


Click "START MEAL 1" to start the meal timer. The color remains green util the max. meal duration is reached. At that moment, the app also draws your attention with a beep and/or a vibration (can be muted in the Settings):

Even though the message asks you to finish the meal, the timer doesn't stop until you press "FINISH MEAL 1". However, if the meal reaches an hour, the timer will stop automatically with a very angry message: "You have been eating for 1 hour already! That is unacceptable, stop eating NOW!!! The meal has been marked as finished".


Click "FINISH MEAL 1". The color remains red util the minimum required time gap between the meals has passed:

Anecdotally, the bottom message was initially intended as an additional service, but during the app testing, that feature was found to be even more important and useful than the timers themselves!


Click on "START MEAL 2" to trigger the same meal duration logic described above for MEAL 1:


Finally, click "FINISH MEAL 2" to complete the today's cycle:

Now you can use the app to count the hours to comply with the minimum 3 hours gap between the last meal and going to sleep (according to rule 4).


If you stop using the app during the EATING WINDOW (for example, start a meal, but don't finish it, or finish MEAL 1 but don't start MEAL 2), the app is intelligent enough to account for that situation. The app determines and implements the best possible solution, which makes sense for each situation, and explains the remedial actions which it took. This enables the user to be aware of what happened and how the timers are counting when the app is reopened. You will find more details about that in Questions & Answers.

Questions & Answers

Can I prevent the button from being pressed by mistake?
Yes. In the Settings, there is an option to toggle "Hold button for half a second to avoid accidental click".

Is it possible make the timers display seconds?
Yes. In the Settings, there is an option to toggle "Show seconds". However, this is a bad idea because when eating, you should be focused on enjoying your food and watching the seconds will draw away your attention. Even a few minutes less or more here and there make no difference, to say nothing of seconds.

Is it possible to select in the Settings such a combination of max. meal length and min. gap between meals, that their total will exceed the selected EATING WINDOW length?
No. You will get a message like "Value rejected due to mismatch. Two meals of 35 minutes each with 4 hours gap between them exceed 5-hours eating window".

Can I see my statistics?
Yes - click the eye icon. The Statistics screen displays average duration of meal and eating window for the last 7, 30 and 365 cycles as well the number (and %) of days with OMAD (one meal a day) for these periods. The screen also shows the details of the previous cycle.

Can I use the app to measure multi-days fastings I practice sometimes?
Yes. If you don't start MEAL 1 for 24 hours or more, the FASTING WINDOW timer displays days in addition to hours and minutes.

Why is the EATING WINDOW timer not shown during MEAL 1?
It would display the same time as the meal timer.

I have set my maximum EATING WINDOW as 4 hours. Why does the FASTING WINDOW timer show 16 hours rather than 20?
The progress bar, labeled as 16 hours, only shows where you are in approaching the minimum required 16-hours fast. When that goal is achieved and 16 hours are over, the progress bar and the 16-hour label disappear. After that, you can start eating at any moment - you are not forced to fast 20 hours. The 4-hours EATING WINDOW can float during the day, so the actual fasting could be shorter, than 20 hours, in one day, and longer in another.

What if I click the button to start a meal, but then, by any reason, change my mind and decide not to eat now? Can I delete the just started meal?
No. That situation will never happen if you obey this simple, but important rule: click "START MEAL x" only once you've started eating (after 2-3 chewings).

Let's say, I clicked "FINISH MEAL x", but after that, I couldn't keep myself from eating something else. Can I correct the meal's finish time?
No. In fact, that is not needed. Excessive accuracy is absolutely irrelevant - intermittent fasting is not math. This protocol is only a recommendation and not an absolute law. So, the sky will not come crashing down if you ate 37 minutes instead of 30, or fast for 15 hours instead of 16 (just don't make it a habit). That also means, that if your hands are dirty after eating, take your time and wash and dry them, and only then click "FINISH MEAL x" with a clean finger without a need to rush.

What if I finish MEAL 1, don't start MEAL 2, and the EATING WINDOW comes to its end (is over)?
If the current EATING WINDOW is 4, 5, 6 or 7 hours, it is automatically prolonged to the maximum possible 8 hours (to give you the last chance to eat this day). When that happens, the label of the progress bar changes, for example, from "5 h" to "8 h (extended from 5 h)". In fact, that jump occurs even earlier - at the moment when you don't have enough time to complete MEAL 2 while still staying in the EATING WINDOW. For example, if you pre-programmed a 30 min meal and a 5-hour EATING WINDOW, the actual EATING WINDOW is prolonged to 8 hours when its duration reaches 4 hours 30 minutes and you have not started MEAL 2. However, if the EATING WINDOW is already 8-hours, it cannot be prolonged anymore, therefore the day is automatically marked as OMAD just in the moment when 8 hours are reached. In this case, you are still able to start MEAL 2 a moment before - even though you will exceed the maximum allowed EATING WINDOW. If you didn't use that opportunity and didn't start MEAL 2, then, when you reopen the app after that, you see this message: "The previous cycle was recorded for statistics as OMAD. Since you didn't start meal 2 during the 8 hours eating window, the finish time of meal 1 was used as the start time of the current fasting window".

Can I mark the day as OMAD manually after MEAL 1 if I am not planning to have MEAL 2?
Yes. In the menu, select the option "Only one meal today". But, as it was mentioned above, you don't need to to that as the app will recognize the day as OMAD automatically if you don't eat second meal before the 8 hours EATING WINDOW ends.

The bottom message says: "Wait 18 minutes until next meal. Start it at 7:34 PM. Eating window ends at 7:34 PM". The timer is green. How does it permit to start a meal just when the EATING WINDOW ends?
That is absolutely OK since the preset EATING WINDOW is shorter than the maximum 8 hours. If you don't eat until the displayed time minus the preset meal length, the EATING WINDOW is automatically prolonged to 8 hours as described above.

The app says, that I can break fast at 11:30 AM. It's already 11:30 AM, but the color is still red, and the message still says: "Next meal: 11:30 AM or later. Wait 1 m". I am waiting, waiting - nothing happens! Finally, it becomes green and the message disappears - just a moment before 11:31. Is it a bug?
No. That is the price we pay for not showing seconds in the bottom message in order to keep it simpler. The next meal time might have actually been 11:30:57 AM, but you saw only 11:30 AM. Once again - seconds are absolutely unimportant since the periods' durations are only a very approximate recommendation. If you are hungry SHORTLY before the permitted time, and find yourself looking at the app waiting to green, stop doing that and simply eat!

When are the timers red?
Only in four situations (but you don't need to learn them - simply don't eat on red):
1. FASTING WINDOW has lasted for less than 16 hours.
2. Meal has lasted for too long.
3. Too little time has passed since the end of MEAL 1 to start MEAL 2.
4. You don't have enough time to complete MEAL 2 while staying within the the 8-hours EATING WINDOW (for example, the EATING WINDOW ends in 20 minutes, but the max. meal length is set as 30 minutes). You are not blocked from starting MEAL 2 in that situation (even though you will exceed the max. allowed EATING WINDOW).

Does the app warn the user if they try to make an incorrect action?
Yes. Undesirable or suspicious actions require an approval via a confirmation popup window with a warning message which clearly explains what is wrong or suspicious. Absolutely prohibited actions are blocked. For example, you cannot start MEAL 2 earlier than 2 hours after MEAL 1 (you will get an error message) but you can still start MEAL 2 earlier than the pre-programmed minimum gap between meals (3, 4 or 5 hours) if you confirm your intention through a message (as long as it's longer than 2 hours, of course).

Why does the app allow the user to proceed with the undesirable actions (through a confirmation window) rather than blocking it (as it blocks the prohibited actions)?
The app cannot force humans to act correctly in real life. Even if the user chooses to occasionally break from the protocol, the app still records the actual time to correctly calculate the next time period. For example, the app allows the user to break a fast even if they have been lasting for less than 16 hours (but not if it's shorter than 8 hours). Why? There could be different circumstances in our lives, such as a very important business breakfast, or a long-distance flight which moves the cycle in a few hours.

If a meal reaches one hour while the app is open, it's marked as finished by force (and prompts the angry message). What if I start a meal, and then close the app without hitting the button when the meal is finished? In other world, if a meal reaches one hour when the app is closed.
The meal is automatically finished by force even when the app is closed. Its time is arbitrary set as one hour. Probably, in reality, the meal was shorter, but the app counts it as the worst case scenario since it's better to make the next phase (the between-meals gap or the FASTING WINDOW) longer than necessary rather than shorter. When you reopen the app after that, the following message pops up: "You didn't mark your most recent meal as finished. That was done automatically when the meal time reached one hour. The AFTER MEAL 1/FASTING WINDOW timer is now counting from that moment".

Why does the application have such an ascetic appearance?
Its purpose is not to impress you with the beauty of the pictures. The application is purely utilitarian - it's all about extreme clarity and ease of use. Nothing extra. The beauty is in the algorithms!


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