Presets on this clock

The hours are a number you chose

The circle fills toward the hours you picked. Filling up only means you hit that number. It does not mean your body changed. As hours pass, the timer shows names such as fat-burning. That name follows the hours on the clock. It is not a lab result. What the stages on the timer mean lists each name and what it is not.

If you have not picked hours yet, start with the gap you already have from dinner to breakfast. Use 16:8 or Open on this timer when you already know how long you mean to go.

What each button does

16:8 means 16 hours of fasting, then about 8 hours of eating. That is the usual first pick on the online fasting timer. The 16:8 page starts with 16:8 already chosen. The button does not choose when those 8 eating hours sit. Noon to 8pm and 10am to 6pm are both 16:8. Fit the eating hours to your sleep and meals.

18:6 means 18 hours of fasting and 6 hours of eating. It is the same kind of button as 16:8. It is not a better 16:8.

OMAD on this timer is about 23 hours of fasting and one meal. The OMAD page starts with that already chosen. OMAD is not a stricter 16:8. It is one meal, and a hard first try for most people.

24h, 36h, and 48h are one long fast with no meal in the middle. A 48 hour fast is not two 16:8 days. Use them only if you already meant to go that long. They are not what you do after 16:8 feels easy. If you already mean more than a day, start with Before a longer fast.

Open has no finish time. The circle does not fill up, because there is no number to fill toward. You can keep counting. That does not mean you should go longer.

Custom is hours or days you type yourself. Want 12 hours or 14 hours? Type them here. You can stay at 12 or 14. You do not have to switch to 16:8.

Three pages, one timer

The online fasting timer lets you pick any hours. History stays on this phone or computer until you clear it.

The 16:8 page and the OMAD page are the same timer. They just start with that button already chosen. Same history, same End Fast button. They are not a different app.

Wrong hours, or you started late

If you tapped the wrong hours, tap Change mode under End Fast. When you started stays the same. Hours already counted stay the same. Only the hours you are aiming for change.

If you forgot to start when you stopped eating, tap Edit Start Time next to the start time. Set when you actually stopped. You cannot pick a time in the future.

Stopping early is still a finished fast. Do not hide it. Do not start a longer fast next to make up for it. If you feel dizzy, confused, faint, or have chest pain, stop. Eat. See When to stop a fast.

What this is not

This is not a diet plan and not a ranking of 16:8 vs OMAD. It is not a 72-hour challenge, and this timer does not weigh you.

Using the timer

Open the online fasting timer. Tap the hours that match the plan you already have. Typing 12 hours in Custom is a full plan. Start when you stop taking calories. Tap End Fast when you eat, including when you eat early.

What to read next

The list of fasts you already finished is History on this clock. The button with no finish time is Open on this clock.

For this week, pick hours you can keep. Tap End Fast when you eat. Skip forum threads about magic hours.