Fasting timer
Keep track of time in a way that works for you.
Your timer settings
The target is a planning aid. You can finish or discard a session at any time.
Eating-window calculator
See when a chosen eating window opens and closes.
Choose a start and length
How the times are calculated
The window closes after the number of hours you choose. The remaining hours in a 24-hour cycle fall outside that window. This is time arithmetic, not a recommendation for how long to fast.
Schedule calculator
Find a start or end time for a duration you choose.
Calculate from a date and time
Planning note
Times use your device’s local time zone. If a clock changes for daylight saving time, the displayed end is calculated from elapsed hours.
Weekly planner
Sketch out start times without setting a rigid rule.
Each day’s end time appears underneath its start time. Leave a day blank if you are not planning one.
History & water
Personal notes stay in this browser on this device.
Fasting sessions
Water log
Log what you drink today. This tracker has no prescribed target.
Fasting guides
Understand the terms and use the tools thoughtfully.
These tools provide general information and time calculations, not medical advice. Talk with a healthcare professional first if you have a medical condition, take medication, are pregnant or breastfeeding, are under 18, or have a history of disordered eating. Stop if you feel unwell.
What is an eating window?
An eating window is simply the part of the day when you plan to eat. For example, a first meal at noon and an eight-hour window gives a closing time of 8 p.m. The calculator shows the clock times; it cannot tell whether a schedule is appropriate for you.
What does the fasting timer measure?
The timer counts elapsed time from when you press Start. It continues using the saved start time even if you close the tab. You can end early, save the actual elapsed time, or discard the session. Reaching a target is not a measure of health or success.
What does the evidence say?
Research on time-restricted eating continues, and results vary by study and person. Longer-term effects are still being studied. A routine also needs to leave room for adequate food, sleep, and everyday life. For background, read the National Institute on Aging overview.
When should someone get individual advice?
Fasting can interact with medical care, particularly diabetes treatment and medicines that affect blood sugar. Do not change medication timing based on a calculator. The NIDDK discusses fasting and diabetes safety; a clinician who knows your situation can help you evaluate your options.
Using the weekly planner
Pick a duration and adjust each day independently. The displayed end time rolls into the next day where needed. The small bars show when each planned interval falls during a 24-hour day; they are a visual summary of your entries, not a score. Days without a start time stay empty.
Questions people often ask
Does coffee or tea count?
What someone includes during a fasting period depends on the reason for fasting and any medical guidance they follow. This timer does not classify drinks or food, and it does not offer instructions for a medical fast.
Will closing the page stop the timer?
No. Its start time is saved in this browser. When you return on the same device and browser, elapsed time is calculated from that saved start time. If you clear browser storage or use another browser, the record may not be available.
Should I keep going if I feel unwell?
No timer target should override how you feel. End the session and seek appropriate medical help if symptoms concern you. For decisions about fasting with a health condition or medication, speak with your healthcare professional.
Further reading
National Institute on Aging: calorie restriction and fasting diets
NIDDK: intermittent fasting and type 2 diabetes
Explore the guides
Privacy
Timer sessions, plans, and water entries are stored only in this browser’s local storage. They are not synced between devices. Clearing your browser data can erase them.