Your fasting window, with real times
Pick your fasting protocol and the time of your first meal, and we tell you exactly your eating window and your fasting window. No mental maths: just read the schedule and you know when to start and when to stop. Fasting works through the discipline of the schedule, but what decides the result is still what you eat inside that window.
Eating window · 8 h eating
12:00 – 20:00
Fasting window · 16 h fasting
20:00 – 12:00 (next day)
You can know all this every day with Renzy
Fasting sets the WHEN; what you eat in the window sets the result. Renzy tracks your calories and protein with a photo.
Continue with my planFree. You pick up where you left off — nothing to repeat.
Guidance only. Intermittent fasting is not for everyone (pregnancy, diabetes, eating disorders, some medications): consult a professional.
Stop looking things up in tables
Photograph the plate and the app gives you calories and macros in seconds — no weighing, no searching.
Next time you are unsure about a plate, photograph it instead of looking it up. It is faster than reading the table.
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How is the fasting window calculated?
Intermittent fasting splits the day into an eating window and a fasting window. The calculator takes your protocol and the time of your first meal, and gives you the exact hours: when the window opens, when it closes, and when the fast ends. 16/8 is the most common because it fits an ordinary day — skip breakfast, eat between 12:00 and 20:00 — while 14/10 is gentler and 18/6 or 20/4 tighten it considerably. One thing worth being clear about: fasting is a schedule, not a mechanism. It helps people who find it easier to eat less within a window, and does nothing special for those who simply eat the same calories in fewer hours.
Intermittent fasting schedules: examples
The actual clock times, which is what people are really after when they type "16/8". The window does not have to start at noon: moving it earlier — eating between 10 and 18 — fits the circadian rhythm better and usually suits early risers. Pick the one you could repeat on an ordinary Tuesday.
| Pattern | Eating window | Who it suits |
|---|---|---|
| 12:12 | 08:00 – 20:00 | First step, barely noticeable |
| 14:10 | 09:00 – 19:00 | Comfortable entry |
| 16:8 | 12:00 – 20:00 | The classic |
| 16:8 | 10:00 – 18:00 | Earlier window |
| 18:6 | 13:00 – 19:00 | With experience |
| 20:4 | 15:00 – 19:00 | Strict, not for every day |
The patterns are conventions of use: no health body publishes official schedules. The benefit of moving the window earlier comes from early time-restricted eating trials (Sutton et al., Cell Metabolism, 2018). These are examples, not a prescription. Fasting is not right for everyone: if you are pregnant, breastfeeding, have a history of disordered eating or take medication, check with a healthcare professional first. These are reference ranges for healthy adults, not a diagnosis or individual advice.
FAQ
What is 16/8 fasting?
Sixteen hours without eating and an eight-hour eating window, usually by skipping breakfast and eating between roughly midday and 20:00. Most of the fast is spent asleep, which is why it is the protocol people stick with for longest.
Does intermittent fasting help you lose weight?
It helps if it makes you eat less overall, and trials comparing it against continuous calorie restriction with the same deficit find similar results. So it is a useful tool for some people and irrelevant for others — there is no fat-burning switch that flips at hour 16.
What can I have during the fast?
Water, black coffee, plain tea and any zero-calorie drink. A splash of milk in coffee will not undo anything meaningful. What breaks the fast in a way that matters is anything with a real calorie load — juice, sugary drinks, or the biscuit that comes with the coffee.
Which fasting protocol should I choose?
The one that fits your life, because adherence is the whole point. If you are starting out, 14/10 is easy to hold. 16/8 is the usual middle ground. Tighter windows like 20/4 make it hard to hit your protein and are worth a specific reason before trying.