Fasting timer

Pick a planned length, from 12 to 24 hours, and press start. If your last meal was earlier, enter that time instead and the timer starts from there. The big number is how long you have been fasting; underneath are the time left, the planned end and how far through you are. When the planned time is reached the timer keeps counting, so you can see the real length of the fast. Press end when you eat, and the last fast is shown next time you open the page.

The start time is kept in this browser's local storage, so closing the tab or the browser does not stop the clock. Nothing is sent to us or anyone else, and there is no account. Clearing your browser data clears the timer.

Most intermittent fasting plans are named by hours fasting to hours eating in a day. The timer offers the usual ones:

They answer different questions. The intermittent fasting calculator plans the day: from your first meal and a schedule, it works out when the eating window closes and how that sits against bedtime. This timer runs the clock on the fast you are in now. Plan with the calculator, then start the timer when you finish eating.

Fasting is not safe for everyone. NIH MedlinePlus Magazine says it is not safe "especially for those with health conditions like diabetes, kidney disease, or heart-related issues," and advises talking with a doctor or other health care provider before you try it. It also notes that much of the promising research is in animals, and more research is needed in people before the benefits and risks are fully understood.

A doctor can look at your health history and any medicines you take, which this page cannot. It only keeps time; it cannot tell whether a fast is right for you.

A timer helps with one fast. Whether the schedule holds across a month is a different record. In BeHabitual you can track it as a daily habit, with its own days, and see in the Month view which days it held and which it did not, next to sleep and anything else you track.