About FastingCalculator.com
We built this site because the tools available for intermittent fasting tracking were either buried inside apps requiring sign-ups, or simplified to the point of being inaccurate. This one is free, precise, and based on peer-reviewed research.
What FastingCalculator.com Does
Our fasting calculator takes your last meal time and chosen protocol — 16:8, 18:6, 20:4, OMAD (23:1), or a custom fasting window — and calculates your precise fast-end time, eating window duration, hours elapsed since your last meal, and an estimated calorie burn during the fasting period.
The calorie burn estimate uses a Mifflin-St Jeor resting metabolic rate approximation, validated by the Academy of Nutrition and Dietetics. The fasting window calculations are based on time-restricted eating (TRE) research by Dr. Satchin Panda at the Salk Institute for Biological Studies, whose circadian rhythm work established the physiological basis for intermittent fasting protocols.
Beyond the calculator, we publish guides, comparisons, and evidence-based articles on intermittent fasting protocols. Every factual claim links to or cites a peer-reviewed source — no speculation, no fad-diet language. See our fasting guide library for a full list of topics.
Precision First
Our fasting window calculations handle 24-hour arithmetic correctly — including overnight windows and midnight crossings that simpler tools get wrong. Every output has a formula behind it.
No Barriers
No account required. No email address. No premium tier. The calculator works in a single page load with zero tracking beyond standard analytics. That's intentional — tools should be tools.
Research-Backed
Our methodology cites Dr. Satchin Panda's TRF research, Mark Mattson's NIH work on metabolic switching, and the Mifflin-St Jeor RMR equations. We don't publish claims we can't source.
Educational Content
The blog covers protocols, safety, exercise timing, nutrition, and common mistakes — written to reflect what peer-reviewed research actually shows, not what's trending.
How We Research
Every article draws from PubMed-indexed studies, systematic reviews, and meta-analyses. We prioritize randomized controlled trials and distinguish established findings from preliminary research.
Regular Updates
Fasting research is active and evolving. We review and update our calculator methodology and content when meaningful new research changes the picture. Check lastUpdated dates on all pages.
Who Built This
FastingCalculator.com is an independent tool site focused exclusively on intermittent fasting. We don't sell supplements, promote specific meal plans, or accept sponsored content that might bias our recommendations. Our only goal is to give you accurate information and a reliable tool to plan your fasting schedule.
We're practitioners as well as builders. The protocols on this site — 16:8, 18:6, OMAD — are ones we've tested personally and verified against the published literature. When the research says something is effective, we say so. When it says something is preliminary or contested, we say that too. See our individual articles for citations.
Medical disclaimer: This calculator and all content on this site are for informational purposes only and do not constitute medical advice. Intermittent fasting is not appropriate for everyone — particularly pregnant and breastfeeding women, people with eating disorder histories, those on certain medications, and people with metabolic conditions. Consult a healthcare provider before starting any fasting regimen if any of these apply to you.
Get in Touch
Found a calculation error, have a question about a protocol, or want to suggest a topic for a new guide? We read every message.
contact@example.com