Intermittent Fasting Calculator
Calculate your intermittent fasting schedule. Choose your protocol (16:8, 18:6, 20:4, and more) and eating start time to get exact fasting and eating windows.
Part of our Health Calculators collection.
Intermittent Fasting Calculator
Free online calculator
When you want to break your fast each day
Results update automatically as you type
How to Use This Calculator
- 1
Choose your fasting protocol (16:8 is the most popular).
- 2
Enter the time you want to start eating each day.
- 3
Your exact eating and fasting windows are calculated instantly.
- 4
Set a daily reminder using the times shown.
How Fasting Windows Are Calculated
Eating End = Eating Start + Eating Hours Fasting Window = Remaining 24 hours For 16:8 starting at noon: eat 12:00 PM – 8:00 PM, fast 8:00 PM – 12:00 PM (next day).
Example Calculation
Example: 16:8, eating from noon
Inputs
protocol: 16:8eatStartTime: 12:00
Result
Eat: 12:00 PM – 8:00 PM | Fast: 8:00 PM – 12:00 PM
16:8 starting at noon: 8-hour eating window noon–8 PM, then 16 hours fasting.
Frequently Asked Questions
What's the best IF protocol for beginners?
Most beginners start with 14:10 or 16:8. The 16:8 is the most researched and widely used.
Does coffee break a fast?
Black coffee (no milk, sugar, or cream) is generally acceptable during a fasting window.
What is the 5:2 method?
The 5:2 method involves eating normally 5 days and restricting to ~500 calories on 2 non-consecutive days. Different from daily time-restricted eating.