Last updated: March 2026
What Is the Intermittent Fasting Timer?
The Intermittent Fasting Timer is a free online tool that tracks your fasting and eating windows with a live countdown, progress ring, and body milestone notifications — no signup, no app download required. Choose from popular protocols like 16:8, 18:6, 20:4, or OMAD and start timing your fast instantly.
Intermittent fasting is practiced by an estimated 24% of American adults, making it the most popular dietary approach in the US according to the International Food Information Council's 2024 survey. Dedicated fasting apps like Zero and Fastic require accounts and push premium subscriptions. This tool gives you the core timer functionality — free, instantly, in your browser.
The timer shows what's happening in your body at each fasting stage (blood sugar normalization at 4 hours, ketosis onset at 12 hours, autophagy at 16+ hours), logs completed fasts, tracks your streak, and notifies you when your eating window opens.
How to Use the Intermittent Fasting Timer
Step 1: Select your fasting protocol — 16:8 is the most popular for beginners, or set a custom split if you have a specific schedule.
Step 2: Click "Start Fast" when you stop eating. Or backdate the start time if you already stopped eating earlier (e.g., you finished dinner at 8pm and it's now 10pm).
Step 3: Watch the progress ring fill as your fast progresses. Read the body milestone notifications to understand what's happening physiologically at each stage.
Step 4: When the eating window opens, you'll see a notification and the timer switches to your eating countdown. Start your next fast when you're done eating, or let the cycle complete automatically.
Step 5: Track your streak and total fasting hours in the log section. Every completed fast is recorded for your session.
Key Features
Live Progress Ring. A circular SVG ring fills as your fast progresses, with gradient colors that shift from blue-purple during fasting to green during your eating window. The center displays elapsed time, time remaining, and completion percentage.
Body Milestones. At 4, 8, 12, 16, 18, and 24 hours, the timer displays research-backed information about what's happening in your body — from blood sugar normalization to ketosis onset to autophagy activation.
Backdate Support. Already started fasting? Set your actual start time and the timer immediately shows accurate elapsed time. No need to remember to start the timer the moment you stop eating.
Browser Notifications. Get notified when your eating window opens, even if the tab is in the background. Never miss a window transition.
Fast Log and Streaks. Every fast is logged with duration, protocol, and completion status. Track your streak and total fasting hours to stay motivated.
Frequently Asked Questions
What is the best intermittent fasting schedule for beginners?
16:8 is the most popular starting point — fast for 16 hours and eat within an 8-hour window (e.g., skip breakfast, eat from noon to 8pm). It's manageable because 7-8 hours of fasting happen while you sleep.
How many hours of fasting before ketosis begins?
Ketosis typically begins around 12 hours into a fast, when your body depletes its glycogen stores and starts burning fat for fuel. By 16-18 hours, fat oxidation rates increase significantly. Individual timing varies based on activity level and diet.
What is autophagy and when does it start during fasting?
Autophagy is your body's cellular recycling process — damaged proteins and organelles are broken down and reused. It begins ramping up around 16-18 hours into a fast and increases significantly at 24+ hours. It's one of the primary health benefits of extended fasting.
Is it okay to drink water during intermittent fasting?
Yes — water, black coffee, and plain tea are fine during the fasting window. They contain zero calories and don't break your fast. Avoid anything with calories, artificial sweeteners (debated), or cream during fasting hours.
How do I track my intermittent fasting for free?
Use this timer — select your protocol, start the timer when you begin fasting, and the tool tracks your progress, shows body milestones, and logs your completed fasts. No app download or account needed.