Skip to main content

Intermittent Fasting Tracker — 16:8 / OMAD / 5:2 / 36h Timer with Body Stages

Intermittent fasting tracker — 16:8 / 18:6 / 20:4 / OMAD / 5:2 / 36h timer with stages and history log.

  • Runs locally
  • Category Calculator
  • Best for Getting a realistic range before a purchase, plan, workout, or schedule decision.
Health note — pregnancy, type 1 diabetes, history of eating disorders, low blood pressure, or anyone on glucose- or blood-pressure-lowering medication should consult a doctor before fasting. This tool is for tracking, not medical advice.

Set up your fast

16 h
Jun 13, 01:28 AM

Auto-set to your local time. Override to back-date a fast.

Status

Fasted
14h 00m
Remaining
1h 59m
Target
16 h
88%

Current body stage

Transition to fat oxidation

Liver glycogen is nearly depleted; the body shifts toward burning fatty acids and producing small amounts of ketones. Mild hunger waves come and go. (Anton 2018, Obesity Reviews.)

  1. 0–4 h
    Digestion
  2. 4–12 h
    Glycogen burn
  3. 12–18 h
    Transition to fat oxidation
  4. 18–24 h
    Ketosis onset
  5. 24–48 h
    Autophagy upregulation
  6. 48+ h
    Deep autophagy & GH surge

History

No fasts logged yet. Save your first one when you reach (or pass) your target.

What this tool does

Free intermittent-fasting tracker that times your fast, tells you which physiological stage your body is in, and logs every completed fast in your browser so you can see streaks and averages without signing up for anything. Pick a protocol — 16:8, 18:6, 20:4, OMAD (23:1), 5:2 (24 hours), 36-hour Monk Fast, or a custom window — enter the time of your last meal and the tracker shows current fasted hours, hours remaining, a progress bar, and the stage your body has entered: digestion (0–4h), glycogen burn (4–12h), transition to fat oxidation (12–18h), early ketosis (18–24h), autophagy upregulation (24–48h), and deep autophagy past 48 hours. Every stage is annotated with what is happening at the cellular level and at least one study reference, so this is not vibes-based. Completed fasts are saved to localStorage and aggregated into current streak, total fasts, and average fast length. Nothing is uploaded, no account required. Read the medical disclaimer at the top before you start — pregnancy, type 1 diabetes, history of eating disorders, low blood pressure, or anyone on glucose- or blood-pressure-lowering medication should talk to a doctor first.

Tool details

Input
Numbers
The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
Output
Live result
The result area focuses on usable output, with copy, download, or preview actions when supported.
Privacy
Browser-side processing
The main tool logic does not call an external API, so inputs normally stay in the current tab.
Save / share
Local preference storage
Preferences, history, or drafts are saved in this browser without an account.
Performance budget
Initial JS <= 22 KB
No WASM budget is declared, keeping the tool quick to open on mobile.
Best fit
Calculator · Student
Category and role tags drive related tools, internal links, and quick fit checks.

How to use

  1. 1. Input

    Paste or drop your content into the tool panel.

  2. 2. Process

    Click the button. All processing is local in your browser.

  3. 3. Copy / Download

    Copy the result or download to disk in one click.

How Intermittent Fasting Tracker — 16:8 / OMAD / 5:2 / 36h Timer with Stages fits into your work

Use it for fast estimates, comparisons, and planning numbers before you make the final call.

Calculation jobs

  • Getting a realistic range before a purchase, plan, workout, or schedule decision.
  • Comparing scenarios by changing one input at a time.
  • Turning rough assumptions into a number you can discuss.

Calculation checks

  • Double-check units, dates, rates, and rounding assumptions.
  • Treat health, finance, tax, and legal outputs as planning aids, not professional advice.
  • Save the inputs that produced an important result so you can reproduce it later.

Good next steps

These links move the current task into a more complete workflow.

  1. 1 BMI Calculator Body Mass Index calculator with WHO + Asian classifications — metric and imperial — browser-only Open
  2. 2 Weight Loss Tracker & Calorie Deficit Calculator Weight loss tracker — set target, log daily weight, see trend, project goal date with real calorie math. Open
  3. 3 Calorie Calculator Calorie calculator — daily calorie needs (BMR + TDEE), weight loss/gain targets, macro breakdown. Open

Real-world use cases

  • Pushing breakfast back to ease into your first 16:8 week

    You finish dinner at 8pm and usually eat cereal at 7am, which is already an 11-hour overnight fast. To hit 16:8 you only need to delay breakfast to noon. Enter your 8pm last-meal time, watch the timer cross hour 12 mid-morning into "transition to fat oxidation", and you have proof you only added five hours, not a heroic effort. Seeing hours-remaining shrink from 8 to 2 keeps you from caving at 10am.

  • Knowing whether a 20-hour fast actually reached ketosis

    You did a long workout yesterday afternoon and started a 20:4 fast at 6pm. Because glycogen was already low, you want to know if hour 18 to 24 likely put you in early ketosis. Open the tracker, set the 6pm start, and at 2pm the next day it reads 20 fasted hours in the "early ketosis (18-24h)" band with the BHB-rising note and the Anton 2018 reference, so you stop guessing and break the fast with data.

  • Building a 30-day streak you can actually see

    You have tried fasting on and off for months but never knew if it stuck. Log every completed 16:8 fast and the tracker aggregates current streak, total fasts, and average length from localStorage. After three weeks you see a 19-fast streak and a 16.4-hour average, which is far more motivating than a vague sense of "doing okay". The numbers live only in your browser, so no app nags you.

  • Timing a careful refeed after a 36-hour Monk Fast

    You attempt a 36-hour fast over a weekend and dread the part where you wreck it with a giant pizza. Set the start at Friday 8pm; the tracker shows you crossing hour 24 into "autophagy upregulation" Saturday evening and hitting 36 hours Sunday morning. When it completes you read the long-fast FAQ, start with 250 kcal of broth, and wait 45 minutes before a real meal instead of shocking a slowed gut.

Common pitfalls

  • Counting plain black coffee as "breaking" the fast and skipping it; black coffee and unsweetened tea are fine, it is the splash of cream or oat milk that adds fat and stops the clock.

  • Jumping straight to OMAD or a 36-hour fast in week one; start at 16:8 and only extend after it feels effortless, or you crash on electrolytes and quit by day three.

  • Treating the 24h autophagy mark as a guarantee; the number is extrapolated from rodent studies, so read it as a rough range (hour 18-24) rather than a switch that flips at exactly 24:00.

Privacy

Your fast history lives only in your browser, under the localStorage key toolora_if_log, and your last-meal time stays on this page. The tracker does not put your start time or protocol into the URL, so sharing the page link never leaks your fasting schedule, and no timestamp rides along on an analytics event. Clearing site data wipes the log; if you want a backup, copy the JSON out yourself.

FAQ

Tool combos

Folks in your role tend to reach for these alongside this tool.

Browse all tools for this role
Made by Toolora · 100% client-side · Updated 2026-06-13