Calculators
Intermittent Fasting Calculator
Plan an intermittent fasting schedule: eating window start and end times for 16:8, 18:6, 20:4 or a custom fast.
- Runs in your browser
- Nothing uploaded
The tool
Enter your numbers below. Results update as you type, and nothing leaves your browser.
Everything you enter stays on your own machine. Nothing is sent to us or to anyone else, which you can confirm in your browser network tab.
What people use it for
- Planning a fasting schedule
- Fitting fasting around work or training
- Comparing protocols
- Habit tracking
About this tool
What the Intermittent Fasting Calculator does
Time-restricted eating limits meals to a daily window, such as eight hours eating and sixteen hours fasting (16:8). Choosing when the window starts sets when you stop eating and when the next fast ends. This calculator lays out the daily schedule.
Formula
- Eating window = 24 − fasting hours
- Window closes = first meal + eating window
- Fast runs from window close to the next day’s first meal
Worked example
Using the starting values in the calculator above:
| Input | Value |
|---|---|
| Protocol | 16:8 |
| First meal time (24-hour) | 12:00 |
| Meals in the window | 2 |
| Result | Value |
|---|---|
| Eating window opens | 12:00 |
| Eating window closes | 20:00 |
| Eating window | 8 hours |
| Suggested meal times | 12:00, 19:00 |
How to read the result
Total calories and food quality still matter; intermittent fasting works mainly by making it easier to eat less.
Fasting is not suitable for everyone, including people with diabetes on medication, pregnant people and anyone with a history of eating disorders, without medical advice.
General information, not medical advice. Speak to a qualified health professional before making changes to diet, exercise or treatment.
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Questions
Questions about this tool
The things clients actually want to know — costs, timelines, ownership and what happens after launch.
Eating within an eight-hour window each day and fasting for the other sixteen hours.
Water, black coffee and plain tea are usually allowed.
Studies generally find similar weight loss when calories are matched; choose what you can sustain.
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