Intermittent Fasting Calculator
Calculate your intermittent fasting eating window for 16:8, 18:6, OMAD, 20:4, 5:2 and more. Live countdown timer, fasting benefit stages, and workout tips. Free IF calculator.
What is the Intermittent Fasting Calculator?
16:8, 18:6, OMAD, 5:2 and more — get your eating/fasting window, live countdown timer, fasting benefit stages, and workout timing advice. Built for optimal performance, this tool executes client-side directly in your browser without uploading your sensitive data to external servers.
How to use the Intermittent Fasting Calculator
- Select your Intermittent Fasting protocol (e.g., 16:8 Leangains, 18:6, 20:4 Warrior, or 14:10 Beginner).
- Set the start time of your fast (typically when you finish your final evening meal).
- The tool calculates your fasting target, showing the exact time your feeding window opens the next day.
- Monitor the live countdown timer showing current metabolic fasting phases (ketosis, autophagy, insulin drop).
Example: Planning a 16:8 Fast Starting After Dinner at 8:00 PM
Protocol: 16:8 | Fast Start: 8:00 PM
Fasting Window: 8:00 PM - 12:00 PM (Next Day) | Eating Window: 12:00 PM - 8:00 PM
Helps you maintain strict fasting consistency without guessing when your feeding window opens.
Technical Guide & Privacy Assurance
Zero-calorie beverages like water, black coffee, and unsweetened green tea will not break your fast and help manage appetite during the morning fasting window.
Frequently Asked Questions
What is the 16:8 intermittent fasting schedule?+
You fast for 16 hours and eat within an 8-hour window. For example, eating from 12pm to 8pm and fasting from 8pm to 12pm the next day.
When does autophagy start during fasting?+
Autophagy (cellular cleanup) begins around 12–14 hours into a fast and peaks around 16–18 hours. This is one of the key health benefits of extended fasting.
Is it better to work out fasted or fed?+
Fasted training increases fat oxidation but may reduce strength output by ~5%. Training 1-2h before your first meal is a popular middle-ground strategy.