Intermittent Fasting Calorie Window Calculator
Distribute your daily calories across an intermittent-fasting eating window — calories per meal, protein per meal and how far apart to space them.
How it works
Calories per meal = daily calories ÷ meals · Protein target = weight × 1.6 g/kg · Meal spacing = window ÷ (meals − 1)
Intermittent fasting sets when you eat, not how much — so your daily calorie total still drives weight change. Fitting that total into a shorter window means larger meals, which is why they are spaced across the window and anchored with plenty of protein to protect lean mass while eating in a deficit. A 16:8 pattern is an 8-hour eating window and a 16-hour fast; the tool derives the fast from your window automatically.
Worked example
At 1,800 kcal across 2 meals in an 8-hour window, each meal is about 900 kcal, spaced roughly 8 hours apart, with a 16-hour fast. A 70 kg person targeting 1.6 g/kg needs about 112 g protein a day, or 56 g per meal.
Frequently asked questions
Does intermittent fasting work without cutting calories?
Weight loss still requires an overall calorie deficit. Fasting helps mainly by shrinking the window in which you can eat, which for many people naturally reduces total intake — but eating above maintenance in the window will still add weight.
Why so much protein on a fasting plan?
Eating in a deficit and going long stretches without food both risk lean-mass loss. A higher protein target of around 1.6 g/kg, concentrated into fewer meals, helps preserve muscle.
What does 16:8 mean?
It is 16 hours of fasting and an 8-hour eating window each day — the most common pattern. Setting the window to 8 hours here reproduces 16:8; a 4-hour window approaches one-meal-a-day (OMAD).
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Educational estimate for meal planning, not medical or nutrition advice. Serving thresholds and needs vary by person — check with a dietitian for medical diets.