How to read the numbers
Fasting schedules are written as two numbers that add up to twenty-four: hours fasting, then hours eating. 16:8 is sixteen hours without food and an eight hour eating window. 18:6 narrows the window to six. 20:4 narrows it to four. The ratio is the only thing that changes; none of these schedules says anything about the food itself.
For definitions, evidence limits, and safety boundaries, read intermittent fasting for beginners first.
Longer fasts break the pattern and are named in hours instead. A 36 hour fast covers a full day plus both of the nights on either side of it.
13:11, the gentle start
Thirteen hours fasting, eleven eating. For a lot of people this is close to what an unremarkable day already looks like: dinner at seven, breakfast at eight. That is precisely why it is a good first schedule. It builds the habit of starting and ending a timer deliberately without asking you to change when you eat, so the only new thing is the tracking.
16:8 versus 18:6
These two are closer than the numbers suggest. Both usually mean skipping breakfast; the difference is two hours at one end. On 16:8 the window might run noon to eight. On 18:6 it runs two to eight, or noon to six.
What actually changes is flexibility. An eight hour window absorbs a late lunch or an unplanned dinner without much thought. A six hour window has less give: shift one meal and the other has to move with it. People who move to 18:6 often do so because they were already finishing inside six hours most days and the wider window had stopped doing anything.
If you are choosing between them and have not fasted before, start at 16:8. Narrowing later is easy. Starting narrow and backing off feels like failing at something, which it is not, but it puts people off anyway.
20:4
Twenty hours fasting, four eating. In practice this is one substantial meal and possibly something small either side of it, inside a single block of the afternoon or evening. It is a real change to the shape of the day rather than an adjustment to it, and it takes more planning: four hours does not leave room to reschedule.
It is also the point at which the schedule starts to interact with the rest of your life more visibly. Shared meals, work lunches, and training sessions all have to fit inside or around that window. Plenty of people run 20:4 on some days and a wider window on others rather than committing to it every day.
36 hours
A 36 hour fast runs from dinner one evening to breakfast the day after next. This is a different kind of undertaking from the daily schedules, and it is the one most worth discussing with a healthcare professional first, particularly if you take medication, have a medical condition, are pregnant or breastfeeding, or have any history of disordered eating. Pause supports it as a timer option and makes no recommendation about whether you should do it.
Choosing one, and changing your mind
There is no universally best schedule. If fasting is appropriate for you, a wider window may be easier to fit around daily life than a narrow one. The app cannot decide which pattern is suitable for your health, medication, or nutritional needs.
It is also fine to change schedule by the day. Training days, travel days, and days with dinner plans do not have to look like the rest. Pause lets you pick 13:11, 16:8, 18:6, 20:4, or 36 hours whenever you start a fast, so switching costs one tap and does not reset anything.
Tracking whichever one you pick
Whatever the window, the mechanics in Pause are the same. Start the fasting timer deliberately, watch the time left from the widget or the Live Activity, and end it yourself when you eat. Nothing ends automatically. Completed fasts, your current streak, and the last seven days sit in the history view, so the question you can answer at a glance is the useful one: not how today went, but whether the pattern is holding.