Intermittent Fasting Planner

{{ fastingHours }}h fast · {{ eatingHours }}h eat

First meal at {{ firstMealTimeLabel }} · Cycle repeats daily

{{ plan_days }} day plan {{ startDayName }} start {{ fastingHours }}h fasted window Hydration every {{ hydrationIntervalLabel }}

Focus: {{ goalInsights.title }}

Preset:

Fasting window:

hours

Eating window:

hours

First meal time:

Wake time:

Sleep time:

Goal focus:

Start day:

Plan days:

days

Hydration interval:

minutes

Workout preference:

Weekend shift:

Enable weekend shift

minutes

Check these items:

{{ err }}

Waiting for input — enter your routine above to see the plan.

Day	Eating window	Fasting window	Focus points	Copy
{{ row.dayLabel }} {{ badge.text }}	{{ row.eatingStart }} → {{ row.eatingEnd }} {{ row.eatingEndNote }} {{ row.eatingCue }}	{{ row.fastingStart }} → {{ row.fastingEnd }} {{ row.fastingEndNote }} {{ row.fastingCue }}	{{ row.workout }} {{ row.note }}

Hydration reminders

Applies to each day unless you manually adjust.

{{ tip }}

Tags: Body Metrics , Mindfulness , Nutrition

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Intermittent fasting arranges each day into alternating fasting and eating phases so hormones, appetite cues, and metabolic signals can adopt a stable circadian rhythm.

Longevity research suggests aligning the fast with nighttime rest to lighten hunger during waking hours and preserve energy for daily tasks.

Hydration habits, planned workouts, and weekend flexibility help carry the routine through social meals and training blocks without losing structure.

Treat each schedule as a reflection of how your body responds, make gradual adjustments, and speak with a healthcare professional before extending fasts or pairing them with demanding exercise.

This planner is informational only and does not replace personalized nutrition or medical advice.

Technical Details

The planner models a single participant with a daily fasting duration t_f and an eating duration t_e that must sum to twenty four hours within a tolerance of fifteen minutes, enforcing metabolic balance across the cycle.

Wake, first meal, and sleep anchors arrive in 24-hour HH:MM format, convert to minutes from midnight, and flow through a wrap function that preserves event order even when a fast crosses midnight or the eating window extends past the calendar boundary.

Weekend flexibility applies only when enabled, clamping offsets between negative one hundred eighty and positive one hundred eighty minutes, tagging Saturdays and Sundays with badges, and disclosing whether the shift delays or advances the first meal.

Hydration reminders accept zero to disable scheduling or intervals between thirty and seven hundred twenty minutes, generating at most twenty evenly spaced prompts between wake time and an extended sleep marker, while workout suggestions reflect the chosen training focus.

\begin{matrix} t f + t e & = & 24 hours \\ E start i & = & wrap (t first + Δ i) \\ E end i & = & E start i + t e \cdot 60 \\ H j & = & wrap (t wake + j \cdot I hydr) \end{matrix}

Symbols and units
Symbol	Meaning	Unit/Datatype	Source
t_f	Daily fasting duration	hours	Preset or custom entry
t_e	Daily eating duration	hours	Preset or custom entry
t_first	First meal start time	minutes	HH:MM input
t_wake	Wake time anchor	minutes	HH:MM input
Δ_i	Optional weekend offset on day i	minutes	Advanced toggle
I_hydr	Hydration reminder spacing	minutes	Advanced entry
E^start_i, E^end_i	Eating window bounds on day i	minutes	Derived
F^start_i, F^end_i	Fasting window bounds on day i	minutes	Derived
wrap(x)	Function that normalizes minutes into the current day and annotates cross-day transitions	minutes	Computed

Worked example

Inputs: fasting 16 h, eating 8 h, first meal 12:00, wake 06:30, weekend shift +60 min, hydration interval 120 min.

t f + t e = 16 + 8 = 24

E start Sat = wrap (720 + 60) = 780 min, 13:00

H 1 = wrap (390 + 120) = 510 min, 08:30

Interpretation: weekdays follow a 12:00 to 20:00 eating window, Saturdays begin at 13:00 due to the shift, and hydration cues arrive every two hours until the extended sleep marker.

Validation enforces plan lengths between one and thirty days, hydration spacing of zero or at least thirty minutes, and fasting plus eating totals within a quarter hour of twenty four to preserve circadian consistency.

Validation rules
Field	Type	Min	Max	Step/Pattern	Error Text	Placeholder
Custom fasting hours	Number (hours)	>0	24	0.25 increments	Fasting window must be above 0 hours.	none
Custom eating hours	Number (hours)	>0	24	0.25 increments	Eating window must be above 0 hours.	none
First meal time	Time (HH:MM)	00:00	23:59	HH:MM	Enter a valid first meal time (use HH:MM).	12:00
Wake time	Time (HH:MM)	00:00	23:59	HH:MM	Enter a valid wake time (use HH:MM).	06:30
Sleep time	Time (HH:MM)	00:00	23:59	HH:MM	Enter a valid sleep time (use HH:MM).	22:30
Plan days	Integer	1	30	Step 1	Plan days must be between 1 and 30.	none
Hydration interval	Integer (minutes)	0	720	Step 15 (UI cap 360)	Hydration interval should be 30 minutes or more, or 0 to disable.	none
Weekend shift minutes	Integer (minutes)	-180	180	Step 15	Offsets beyond range are clamped when enabled.	none

I/O formats and rounding
Input	Accepted Families	Output	Encoding/Precision	Rounding
Times (wake, first meal, sleep)	24-hour HH:MM	Schedule rows, chart, JSON	Stored as integer minutes, displayed HH:MM	None
Durations (fasting, eating)	Preset hours or decimal hours	Eating and fasting columns	Hours with up to two decimals	Quarter-hour rounding for custom inputs
Hydration and weekend shift	Integers in minutes	Reminder list, weekend badges	Minutes	Multiples of 15, clamped to limits
Export actions	CSV, JSON, DOCX generated locally	Files with slug plus timestamp	UTF-8 text	Matches on-screen display

Precision policy: decimal separators use a period, custom hours round to the nearest quarter hour, hydration sequences stop at twenty events, and weekend offsets clamp before recalculation.

Networking and storage: calculations, charts, and exports execute in the browser; only the ECharts visualization bundle and the DOCX library load from trusted CDNs, and no entered data leaves the device.

Diagnostics and determinism: identical inputs yield identical schedules, validation blocks rendering until the error list clears, and tooltip initialization reruns when tabs change so controls remain accessible.

Performance and limits: processing scales linearly with up to thirty days, chart rendering defers until the visualization tab opens, and hydration generation short-circuits once prompts exceed twenty to preserve responsiveness.

Privacy and compliance: exported files can reveal personal health routines, so confirm local regulations and share only with trusted professionals.

Assumptions and limitations

Models one individual with a single wake block and a single sleep block per calendar day.
Keeps fasting and eating durations constant across the plan aside from optional weekend shifts.
Hydration reminders assume equal spacing and do not adjust for workouts or bedtime changes.
Goal focus summaries, tips, and rotating cues are curated copy rather than adaptive coaching.
Workout placement ignores training intensity, injury status, or recovery markers.
Heads-up Weekend badges appear only when flexibility is enabled and the offset differs from zero.
Timezone changes and daylight saving adjustments are not modeled.

Edge cases and error sources

Fasting or eating hours set to zero produce blocking validation errors.
Times outside 00:00 to 23:59 fail parsing and stop schedule generation.
Entering hydration intervals below thirty minutes triggers clamping and an alert.
Weekend shifts beyond the allowed range are clamped, which can differ from intended offsets.
Loading the chart tab before ECharts finishes downloading keeps the chart blank until a refresh.

How-to

Pick a fasting preset or switch to Custom in Advanced required.
Enter wake, first meal, and sleep times in HH:MM so the planner can anchor the day time inputs.
Choose a goal focus and optional workout preference to tailor notes coaching.
Open Advanced to set plan length, hydration spacing, and weekend shift if desired optional.
Review alerts and adjust inputs until the error list clears ready.
Explore the Table, Chart, and JSON tabs, then copy or export the format you need output.

Example. Select the 16:8 preset, set wake to 06:30, first meal at 12:00, sleep at 22:30, enable a +60 minute weekend shift, and hydration reminders every 120 minutes to see weekend eating windows slide to 13:00 with steady two hour hydration cues.

Log how you feel across two weeks before tightening the fasting window.
Use the JSON view to archive historical plans for comparison.

FAQ

Is any of my data stored?

No. All scheduling happens in your browser, and exports generate locally without transmitting meal times or goals.

Client-side only.

How precise are the fasting and eating windows?

Presets rely on whole hours, and custom entries round to the nearest quarter hour so the plan respects realistic increments.

Quarter-hour resolution.

What units should I enter?

Times use 24-hour HH:MM, hydration and weekend offsets use minutes, and fasting alongside eating durations use hours.

HH:MM and minutes.

Can I keep working offline?

Yes. Once the page loads, calculations, table views, and exports remain available offline; the chart requires ECharts to have loaded previously.

Offline friendly after first load.

How do I plan a 16 8 intermittent fasting schedule?

Choose the 16:8 preset, align your first meal with midday, set sleep to cover the overnight fast, and adjust hydration reminders to sustain energy.

Example workflow.

What do the weekend shift badges mean?

They mark Saturdays and Sundays where you applied a positive or negative offset, and the table cue explains whether the eating window moves later or earlier.

Shows flexibility.

How should I read the hydration reminders?

Each badge represents a suggested drink time between wake and extended sleep; the list stops at twenty entries to keep the routine manageable.

Even spacing only.

Does this tool cost anything?

No pricing information appears in the interface; consult the main site terms if you need licensing specifics.

Availability can change.

Troubleshooting

No plan appears: resolve the error list first and confirm fasting plus eating equals twenty four hours.
Weekend badge missing: ensure the flexibility toggle is on and the offset is not zero.
Hydration list feels crowded: increase the interval or disable reminders.
Chart stays blank: confirm ECharts finished loading and data exists before opening the tab.
CSV or DOCX export fails: allow downloads and keep the table visible until the export completes.
JSON copy shows stale data: refresh the JSON tab after changing inputs to regenerate the highlighted payload.

Blocking issue: fasting and eating totals must equal twenty four hours within the 0.25 hour tolerance or the planner will not generate a schedule.

Glossary

Fasting window: The portion of each day reserved for zero-calorie intake to support metabolic rest.
Eating window: The scheduled span for meals and recovery nutrition within the twenty four hour day.
Weekend shift: An optional offset in minutes that moves Saturday and Sunday eating windows earlier or later.
Hydration cadence: Evenly spaced hydration reminders between wake and extended sleep to maintain fluid balance.
Goal focus bundle: A curated set of summaries, static tips, and rotating cues aligned with weight loss, metabolic health, or muscle maintenance goals.
wrap(x): Helper that normalizes minute counts across days and appends notes when events roll into the next calendar day.