Fasting Duration
Calculator
Track your fasting progress, calculate eating windows, and plan your intermittent fasting schedule. Free tool for 16:8, 18:6, OMAD, and custom protocols.
How to Use the Fasting Calculator
Enter Your Last Meal
Input the time you finished your last meal or snack. This starts your fasting clock.
Set Your Target
Choose your fasting duration (16:8, 18:6, 20:4, OMAD, or custom hours).
Track Progress
Watch your fasting hours increase in real-time and see when your eating window opens.
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Help others discover this free fasting calculator
Popular Fasting Protocols
16:8 Method
Fast for 16 hours, eat within an 8-hour window. Most popular and beginner-friendly.
Example: Eat 12 PM - 8 PM, fast 8 PM - 12 PM
18:6 Method
Fast for 18 hours, eat within a 6-hour window. More restrictive but effective.
Example: Eat 1 PM - 7 PM, fast 7 PM - 1 PM
20:4 Method
Fast for 20 hours, eat within a 4-hour window. Advanced protocol.
Example: Eat 2 PM - 6 PM, fast 6 PM - 2 PM
OMAD (One Meal a Day)
Fast for 23 hours, eat one meal per day. Most restrictive but powerful.
Example: One meal at 6 PM, fast 7 PM - 6 PM
Ready to track your fasts automatically?
Download Fastmode for iOS and get AI-powered insights, adaptive reminders, and seamless tracking.
Download Fastmode App