The Intermittent Fasting Calculator is a free, no-registration online tool that plans your fasting and eating windows using methods like 16:8, 18:6, OMAD, or custom hours, outputting a visual 24-hour timeline with optional personalized calorie and protein targets.
What is the Intermittent Fasting Calculator?
This web-based tool at intermittentfastingcalculator.org generates a fasting schedule based on your chosen protocol (16:8, 18:6, 14:10, 20:4, OMAD/23:1, or custom hours) and your preferred meal times. You input your last meal and next meal times (or use the current time), and it instantly produces a graphical timeline showing the fasting and eating windows. When you enable Advanced Inputs with gender, age, height, weight, goal (lose weight, maintain, gain muscle), and activity level, it calculates a Daily Calories Goal using the Mifflin-St Jeor equation and a Daily Protein target based on ISSN standards (1.2–1.8 g/kg). No account or signup is required to use any feature.
Key Features
- Multiple fasting protocols — Choose from 16:8, 18:6, 14:10, 20:4, OMAD (23:1), or define custom fasting hours with minute-level precision.
- Personalized nutritional targets — Optional advanced inputs unlock Daily Calories (Mifflin-St Jeor TDEE) and Daily Protein (ISBN 1.2–1.8 g/kg) adjusted for your weight goal.
- Metabolic milestones timeline — The advanced results display physiological phases: Fed State (0–2h), Transition (2–12h), Fat Burning (12–18h), Autophagy Support (18–24h), and Extended Fast (24h+), based on your last meal time.
- 24-hour visual timeline — A real-time hour-by-hour graphic shows your fasting and eating windows, with markers every hour from 00 to 24.
- Export your schedule — Copy the plan as text or export it as an image for sharing or printing.
- No signup or account — All functionality is available immediately without registration, login, or data storage.
Who is it for?
- Beginners trying intermittent fasting for the first time — Quickly set up a 16:8 or 14:10 schedule by entering a meal time and seeing the exact fasting window.
- Experienced fasters who use OMAD or 20:4 — Enter custom hours or select advanced protocols and track metabolic phases like autophagy support.
- Anyone wanting calorie and protein guidance during fasting — Enable Advanced Inputs to receive a TDEE-based daily calorie goal and a protein target tailored to their body metrics and activity level.
- People who need a portable, shareable plan — Export the schedule as text or image to keep on their phone, desk, or fridge.
What can you do with the Intermittent Fasting Calculator?
- Plan your daily eating window — Select 16:8 (fast 16h, eat 8h) and set your first meal at 10:00 AM to see that your eating window runs until 6:00 PM, with the next fast starting automatically.
- Get customized calorie and protein targets — Fill in gender, age, weight, height, goal, and activity level to see a Daily Calories Goal (e.g., 1,749 kcal) and Daily Protein target (e.g., 96g) computed from the Mifflin-St Jeor equation and ISSN standards.
- Track your body’s metabolic stage during the fast — After enabling advanced inputs, view when your body enters fat-burning mode (around 12 hours) and autophagy support (around 18 hours) based on your last meal.
- Compare different fasting methods — Switch between 14:10, 16:8, 18:6, 20:4, OMAD, or custom hours to see how each shifts your eating and fasting timeline without re-entering your personal data.
