OMAD & 20:4 Fasting Timer

Track extreme fasting protocols in real time. Enter your fast start time, pick your protocol, and watch your progress live — your timer survives page reloads.

Your start time and protocol are saved locally in your browser. The timer picks up where it left off after a page reload — no account needed.

Fasting
00:00:00
until eating window opens
0% complete
Eating Window Opens
Eating Window Closes

How it works

Each fasting protocol is defined by two numbers — the fast window and the eat window. Together they always add up to 24 hours. The timer uses your local clock to calculate exactly where you are in the cycle.

OMAD (23:1) Fast 23 h, eat in a single 1-hour window. Most extreme protocol — often one large meal per day.
Warrior Diet (20:4) Fast 20 h, eat within a 4-hour window. Allows a full meal plus small snacks during the window.
18:6 (Lean) Fast 18 h, eat within 6 hours. A strong middle ground between OMAD strictness and 16:8 flexibility.
16:8 (Leangains) Fast 16 h, eat within 8 hours. The most widely practiced protocol — skip breakfast, eat noon–8 pm.

The progress bar fills from 0% to 100% as your fast approaches the eating window. Once the window opens it switches colour and counts down the remaining eat time. After 24 hours the cycle restarts automatically.

Frequently asked questions

What is OMAD and how does 23:1 fasting work?
OMAD stands for "One Meal A Day." The 23:1 protocol means you fast for 23 hours and compress all your eating into a single 1-hour window. During the 23-hour fasting period you consume only water, plain black coffee, or unsweetened tea. The eating window can be placed at any time of day — many people choose dinner (5–7 pm) so the fast ends naturally while they sleep. The timer above calculates your window based on the exact start time you set.
What is the difference between 20:4 and OMAD?
Both are extreme fasting protocols, but 20:4 gives you a 4-hour eating window instead of 1 hour. This makes it possible to have a full meal plus fruit, nuts, or raw vegetables during the window. 20:4 is sometimes called the Warrior Diet (popularized by Ori Hofmekler in 2001). OMAD is stricter: one plate, one sitting. Both protocols produce deep ketosis and autophagy when sustained, but OMAD requires more discipline around meal timing and nutrient density.
Does the timer keep running if I close the tab?
Yes. Your fast start time and protocol are stored in your browser's localStorage immediately when you press Start. When you reopen the page, the timer reads that saved timestamp and recalculates your current position in the fast — so you always see accurate elapsed time and remaining time, even after closing and reopening the browser.
Can I drink coffee or water during the fasting window?
Plain water, sparkling water, black coffee (no milk, no sweetener), and plain tea are generally considered compatible with intermittent fasting because they contain negligible calories and do not meaningfully trigger an insulin response. Bone broth, BCAAs, artificial sweeteners, and milk all have varying evidence — most strict OMAD practitioners avoid anything other than water and black coffee to be safe. This timer tracks time only; dietary choices during your fast are your own decision.
What time should I start my eating window?
The most common approach is to align the eating window with your largest social meal. For 16:8 that typically means noon to 8 pm. For OMAD, a single dinner at 5–6 pm is popular because you fast through sleep and morning hours, which are subjectively the easiest. For 20:4 some people prefer a late-afternoon window (3–7 pm). The "best" time is whatever you can sustain consistently — the timer lets you set any start time so you can experiment without losing track.