Intermittent Fasting Calculator
Fasting and eating window schedule.
Enter your values
Enter the first meal hour (24h) you are working with.
Choose one of: 14:10, 16:8, 18:6, 20:4.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Eating window
- 12:00 – 20:00
- Fast begins
- 20:00
- Fast ends
- 12:00
- Hours fasting
- 16
- Hours eating
- 8
- Fasting hours per week
- 112
Quick answer
Intermittent fasting sets a daily eating window; 16:8 means 16 hours fasting and an 8 hour window.
At a glance
| What it does | Fasting and eating window schedule. |
|---|---|
| Category | Health |
| Inputs needed | First meal hour (24h), Plan |
| Main output | Eating window |
| Cost | Free — no sign-up, no download |
How to use the Intermittent Fasting Calculator
- 1Choose the hour of your first meal.
- 2Pick a fasting plan.
- 3Read your daily eating window.
Inputs explained
- First meal hour (24h)
- Enter the first meal hour (24h) you are working with.
- Plan
- Choose one of: 14:10, 16:8, 18:6, 20:4.
Worked example
Using the values the calculator loads with:
Inputs
- First meal hour (24h)12
- Plan16:8
Results
- Eating window12:00 – 20:00
- Fast begins20:00
- Fast ends12:00
- Hours fasting16
- Hours eating8
- Fasting hours per week112
Frequently asked questions
Does black coffee break a fast?
No — plain coffee, tea and water are fine.
Is 16:8 best?
It is the easiest to sustain; longer fasts offer diminishing returns for most people.
What do I need to enter into the Intermittent Fasting Calculator?
Just 2 values: first meal hour (24h), plan. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Intermittent Fasting Calculator work out the answer?
Intermittent fasting sets a daily eating window; 16:8 means 16 hours fasting and an 8 hour window. The working is shown step by step so you can verify the result by hand.
Is the Intermittent Fasting Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.