Every fasting schedule on one chart
Published fasting charts almost always give you clock times that belong to somebody else. Here is the standard version, anchored to a 7 PM dinner and a night of sleep from 11 PM to 7 AM, with one column those charts leave out.
| Schedule | Fast | Eat | Eating window | Waking fasted hours | Meals it holds |
|---|---|---|---|---|---|
| 12:12 | 12 hours | 12 hours | 7 AM to 7 PM | 4 hours | All three meals, unchanged |
| 14:10 | 14 hours | 10 hours | 9 AM to 7 PM | 6 hours | Late breakfast, lunch, dinner |
| 16:8 | 16 hours | 8 hours | 11 AM to 7 PM | 8 hours | Lunch and dinner |
| 18:6 | 18 hours | 6 hours | 1 PM to 7 PM | 10 hours | Two meals, close together |
| 20:4 | 20 hours | 4 hours | 3 PM to 7 PM | 12 hours | One meal plus a small second |
| OMAD | 23 hours | 1 hour | 6 PM to 7 PM | 15 hours | One meal |
The fifth column is the number that decides whether a schedule survives. With an evening-anchored window, all eight hours of sleep fall inside the fast whichever protocol you pick, so the sleeping hours are constant and only the waking ones change. Moving from 16:8 to 18:6 reads as two hours on paper. In practice it is two more hours awake and fasted, taking you from eight to ten, and it removes a meal slot at the same time. That is why the step feels bigger than the same two hours from 14:10 to 16:8.
Compare protocols on that column rather than on the ratio, and the choice usually makes itself.
Put your own times into the chart
The chart above assumes a 7 PM dinner and a 7 AM alarm. Change either and every row moves. Someone who eats at 9 PM and wakes at 6 AM has a completely different set of windows, and a 16:8 schedule that ends at 1 PM rather than 11 AM, which is the difference between a normal lunch and a very late one.
The planner at the top of this page does that recalculation from your times. It also reports each option's sleep overlap directly, so you get your own version of the fifth column instead of one computed for an average person who does not exist. Every field is optional: give it a duration alone and it returns sensible defaults, add your dinner and each option is checked against it, add sleep and wake times and the overlap appears.
Starting from scratch
If you have not run a fasting schedule before, the useful first question is which meal your day can lose without a fight. For most people that is breakfast, which is why evening-anchored windows are common. For anyone who trains in the morning or eats with children before school, it is dinner, and an early window from 8 AM to 4 PM does the same arithmetic in the other direction.
A common approach is to start at 12:12 or 14:10 and lengthen the fast when the current one stops requiring attention, often after a week or two. Worth saying plainly: no trial establishes a required starting duration or a required pace of increase, so this is a comfort convention rather than a rule. Some people begin at 16:8 and are fine. Others stay at 14:10 permanently, which is a schedule and not a half-measure.
Whatever you pick, run the times through the planner before the first day rather than after. Discovering that a 16-hour fast and an 8 AM breakfast cannot coexist is cheaper as arithmetic than as a week of missed targets.
What the planner computes
The planner computes relationships: "8h of your fast occurs during sleep", "fits your 7:30 PM dinner", "conflicts with your preferred breakfast". It will never tell you a schedule is biologically optimal, because that claim cannot be honestly computed from clock times. When your constraints are mathematically impossible, it says so and shows exactly which lever to move. That is the position this whole site takes:the best fasting schedule is the one you can actually keep.
Why a schedule calculator beats a protocol picker
Most fasting tools start with "choose 16:8 or 18:6", a question that assumes the answer. Real schedules start from fixed points you do not control: when you must be at work, when the household eats, when you can sleep. A fasting schedule calculator worth the name takes those fixed points as input and derives the windows, instead of handing you a generic noon-to-eight and wishing you luck. Each field on the analyzer explains why it is asked, and every one is optional.
When an option fits, one tap on "Use this schedule" hands its boundaries to the timer, so plan and execution stay one system, computed by one engine.
Weekly patterns people actually run
A daily schedule is one option among several, and it is not automatically the strongest. These four patterns cover most of what people settle into, with the honest cost of each.
| Pattern | What it looks like | What it protects | What it costs |
|---|---|---|---|
| Daily | The same window every day | Simplest to remember, no decision to make each morning | Leaves no room for a late dinner without shortening that day |
| Weekdays only | 16:8 Monday to Friday, weekends open | Protects social meals, which is where most schedules break | Monday can feel like restarting each week |
| Split duration | 16:8 on workdays, 12:12 at weekends | Keeps a structure every day without defending it at weekends | Two sets of clock times to remember |
| Two longer fasts | Two fasting days, the rest unstructured | Very little daily admin | The fasting days are harder in isolation |
The weekly planner below lays any of these out day by day and reports your total planned fasting hours and the average per fasting day. No configuration is labeled a compromise. If you are choosing between patterns, the practical questions are which days your calendar genuinely leaves quiet, and which pattern you would still be running in three months. Model both, pick one, and let your history report how it went.
When your work decides your clock
Every schedule above assumes you sleep at night. For shift workers that assumption fails, and most published charts fail with it. The arithmetic itself is unchanged: a 24-hour circle does not care which part of it you sleep in, so a 16-hour fast around daytime sleep works exactly like one around night sleep, and the sleep overlap column still decides how it feels.
What does change is that your fixed points move week to week on a rotating rota, so a single set of clock times will not survive the rotation. The night shift fasting calculator takes shift hours and daytime sleep as its inputs, and the weekly planner below handles a rota by letting each day carry its own window.
Planning frequency honestly
"How often should I fast?" has no universal answer. Studies cover daily time-restricted eating, weekday-only patterns, and one or two longer fasts per week, and the outcomes track overall intake and sustained adherence more closely than the frequency itself. Whatever you model here, the number worth watching afterwards is your own average over a month, which the history view reports without commentary.
One thing the planner will not do is treat a missed day as a broken streak, because a schedule is a plan for a week rather than a test you pass each morning. A fast that ran fourteen hours instead of sixteen is recorded as fourteen hours. If you would rather see streaks, they exist behind the optional Motivation Mode toggle, off by default and entirely your choice.