What this is
Free Fasting Calculator is a free set of tools organized in three pillars. The fasting pillar is the core: calculators for every common protocol, a reverse calculator, a life-aware schedule planner, and a timer that tolerates human error, with local history. The post-diet planning pillar adds the Reverse Diet Calculator, a transparent week-by-week calorie ramp for ending a deficit. The body-measurement pillar adds the ABSI Calculator and the Visceral Fat Calculator, both implementing published, cited research models with their formulas shown. Everything runs in your browser. There is no account, no subscription, and no upsell: the entire product is the free product.
Editorial standards
- No fake precision. We do not claim that specific hours trigger specific biological processes, we do not predict weight loss, and our body-measurement tools report estimates from named published models, never diagnoses, mortality predictions, or invented "levels". Where research is uncertain, we say so.
- No invented authority. No fabricated experts, reviewer credentials, quotes, studies, or proprietary datasets appear on this site. If a claim can't be supported, we soften it or leave it out.
- Calculation, not recommendation. The tools compute schedule mathematics and factual relationships (sleep overlap, meal conflicts). They never rank protocols as medically better or worse.
- Non-judgmental by design. A 14-hour fast against a 16-hour target is recorded as data, not failure. Streaks are optional and off by default.
How it's built
One deterministic, unit-tested calculation engine powers every page: the same code computes a 16:8 window on the homepage, the protocol pages, the timer, and the planner, so results never disagree. The site is static, fast, and works the same on a phone in a kitchen as on a desktop at work. Your data model is deliberately boring: timestamps in your own browser.
Who runs this
Free Fasting Calculator is an independent site, built and maintained by one small team rather than a company with a content department. Nobody here is a doctor or a dietitian, and you will not find a fabricated medical reviewer byline on any page, because inventing one is the standard move in this niche and we would rather say plainly that we do not have one.
What we do have is arithmetic we can show you and sources you can open. Where a page makes a clinical claim, it names the publication behind it and links the full text, usually on PMC or another open archive, so you can check our summary against the paper instead of trusting it. Where the evidence does not settle a question, the page says the evidence does not settle it. That is the whole basis on which we ask you to trust the tools.
How this site is funded
Advertising, once it is running. There is no subscription, no premium tier and nothing held back behind a signup, so ads are what pay for the hosting and the time. We are applying to Google AdSense and no ads are on the site yet. The privacy policy sets out exactly what that will involve and how to opt out of personalised advertising.
Worth saying because it affects what you read here: advertising pays per visit, and that creates an incentive to write pages that sound authoritative whether or not the evidence supports them. Our answer is the editorial standards above, and the easiest way to hold us to them is that we publish the sources. A page that refuses to predict your weight loss earns less than one that invents a number, and we would rather take that trade than have you act on something we made up.
Contact & corrections
Found an error (mathematical, factual, or editorial)? We treat corrections as contributions. Contact the site operator and the page will be reviewed and dated when revised.