Intermittent Fasting Calculator
Results are estimates only and may not reflect your individual needs. This tool is for educational purposes only and is not medical advice.
Choose your IF protocol (16:8, 18:6, 20:4, or 5:2) and get your daily calorie targets.
Your result will appear here
Complete the form and press Calculate IF Plan.
Estimated result
Intermittent fasting is not suitable for everyone. Consult a healthcare professional before starting.
Why use this calculator
Intermittent fasting works by restricting your eating window rather than counting every calorie. This calculator converts your chosen fasting protocol (16:8, 18:6, 5:2, and others) into a clear daily eating and fasting schedule.
How to use this calculator
Enter your details and activity level, then choose your preferred IF protocol. Press Calculate to see your calorie target and eating window details.
What the result means
For time-restricted protocols (16:8, 18:6, 20:4), a mild calorie reduction is applied reflecting the natural reduction from a shorter eating window. For 5:2, normal-day calories match your TDEE and fast days are capped at 500 kcal.
Important limitations
Intermittent fasting is not suitable for people with a history of eating disorders, those who are pregnant or breastfeeding, or those with certain medical conditions. Always check with a healthcare professional before starting.
FAQ
Can I drink water during the fast?
Yes — water, black coffee, and plain tea are generally considered acceptable during fasting windows.
Which protocol is best for beginners?
16:8 is the most popular starting point because it typically just means skipping breakfast.
These estimates are for educational purposes only and are not medical advice. They are not intended for children, teens, pregnancy, eating disorder recovery, or medical conditions.