Calculate. Plan. Track.
A fasting schedule that fits your real life
Calculate your fasting and eating windows, start a reliable timer, and plan a schedule around your sleep, work, and meals. Free, private, and fast: no account, no upload, no exaggerated health claims.
What do you want to do?
Quick calculator
Private by design
Calculations and tracking happen entirely on your device. No account, no cloud, no personal data uploaded. Export or delete your history anytime.
Built for real life
Forgot to start the timer? Ate late? Broke your fast early? Edit it. The tool recalculates instead of treating you like you failed.
No fake precision
We calculate schedules. We don't claim an exact hour when your body "enters autophagy" or promise a number on the scale. What research actually shows varies by person.
One engine, every fasting tool
FreeFastingCalculator.com is a complete fasting toolkit built on a single tested calculation engine. Theintermittent fasting calculatoranswers the everyday question: enter a last meal, get your windows. Thefasting window calculatorframes the same math around window boundaries, and thefasting time calculatoranswers "when can I eat?" directly, with a reverse mode for"when should I stop eating?". Because every page consumes the same engine, a 16:8 window computed anywhere on this site is identical everywhere else, across midnight, daylight-saving changes, and leap days.
Theintermittent fasting timerturns any calculation into a live countdown that survives closed tabs and forgives human error: forgot to press start, ate late, broke early? Edit it, and the timer recalculates instead of scolding. When a fast completes, the eating-window countdown takes over so you always know when the next fast begins, and every session lands in your local history as neutral facts: actual versus target, averages, longest fast. Optional streaks exist behind a Motivation Mode toggle for people who want them, and stay invisible for people who don't.
Thefasting schedule calculatoris where this site goes beyond the usual: give it your wake time, bedtime, work hours, dinner, and workout, and it generates every eating window that fits, with sleep overlap computed, conflicts flagged in plain language, and impossible combinations explained with concrete fixes instead of silence. A dedicatednight shift calculatorhandles schedules that ordinary tools break on, and the weekly planner supports different windows per day, because real weeks aren't uniform.
Everything travels with you, too. Any schedule becomes a share link that carries only two numbers, a start time and a duration, so a partner or friend can open the same calculation without accounts on either side. Calendar export turns your windows into normal events with normal reminders; the print view produces a clean one-page schedule for the fridge; and JSON/CSV export means your history is genuinely yours, portable to any spreadsheet. Delete everything with one button whenever you like; theprivacy pagedescribes exactly how little we could see even if we wanted to, which is nothing.
What you won't find here: predicted pounds, "autophagy unlocked at hour 16" badges, protocol health scores, or invented experts. Fasting research supports modest, honest claims (schedules help some people eat less consistently, and consistency beats intensity), so that is what we build for. The full reasoning behind that editorial position lives on ourabout page, and the concise medical safety note appears beside every tool because a scheduling site should know what it isn't. Calculate. Plan. Track. Nothing else.
Common questions
What is an intermittent fasting calculator?
A tool that turns two inputs (your last meal time and a fasting duration) into your complete schedule: when the fast ends, your eating window, and when the next fast begins. Ours handles every common protocol (12:12, 14:10, 16:8, 18:6, 20:4, OMAD) plus custom durations, and runs entirely in your browser.
Is everything on this site really free?
Yes. The fasting calculator, the fasting timer, the schedule planner, and your history are all free with no account, no trial, and no premium tier. The calculations are arithmetic; charging a subscription for arithmetic is the industry habit we exist to break.
How is this different from fasting apps?
No download, no signup, no upsell, and your data never leaves your device. You get the useful parts of a fasting app (calculator, live timer, corrections, history, weekly planning) without the parts people complain about: accounts, subscriptions, streak guilt, and AI coaching nobody asked for.
Which fasting schedule should I start with?
The one your calendar can hold. Research comparing protocols finds adherence and overall intake matter more than the exact ratio, so start from your life: if mornings need food, look at 14:10; if skipping breakfast is easy, 16:8 is the common default; if you want the gentlest boundary, 12:12. The schedule planner can decide with you, using your actual wake, sleep, and meal times.
Will fasting make me lose weight?
Honestly: it can, for some people, mainly by helping them eat less overall. Studies find results broadly comparable to conventional calorie restriction when intake is similar. No calculator can promise your number, and we refuse to fake one. What we give you instead is structure and honest tracking.
Is my data private?
Calculations and tracking happen on your device. No account exists, no fasting data is uploaded, share links contain only schedule parameters, and you can export or delete your history anytime. The privacy page spells out the details.
Does the site work on my phone?
It is built mobile-first: large touch targets, time inputs that use your phone's native picker, a timer readable at a glance, and layouts that adapt from small phones to wide desktops. Dark mode is the default, and a light mode toggle lives in the header, and your choice is remembered on your device.
Can I fast on a night shift or irregular schedule?
Yes. The night shift fasting calculator is built for exactly that, treating every interval as a point on the 24-hour circle so daytime sleep is handled like nighttime sleep. Rotating patterns can be modeled block by block, and the weekly planner accepts a different window for every day.