Intermittent Fasting Calculator: Plan Your Eating Window
Pick a fasting method and your first meal time to get your eating window, meal times and calories per meal, built around your daily calorie target.
What is intermittent fasting?
Intermittent fasting (IF) means eating only during a set window each day, or eating very little on certain days. It doesn’t tell you what to eat, only when. For many people, a shorter eating window simply makes it easier to eat fewer calories.
Does intermittent fasting help weight loss?
What research shows
- IF leads to weight loss similar to standard calorie counting
- It can make eating less feel easier for some people
- It may cut late-night snacking
What it isn’t
- Not magic: calories still decide fat loss
- Not better than other diets when calories match
- Not a licence to overeat in the window
Intermittent fasting tips
A protein-rich first meal keeps you full through the window. See our protein calculator.
Water, black coffee and plain tea help with hunger during the fast. Our water intake calculator shows how much.
Begin with 12:12 or 14:10, then extend the fast by an hour every few days.
If you lift, try to eat a meal within a few hours after training.
Moving your window for a social meal won’t undo your progress.
Fewer meals means each one needs more protein. Plan with our macro calculator.
Who should avoid intermittent fasting?
- Pregnant or breastfeeding women
- Children and teenagers
- Anyone with a history of eating disorders
- People taking insulin or other blood sugar medication, unless supervised by a doctor
- Anyone who feels dizzy, unwell or very irritable while fasting
Intermittent fasting FAQs
Can I drink coffee while fasting?
Yes. Black coffee, plain tea and water are fine. Milk, sugar and creamers add calories and technically break the fast.
Is 16:8 fasting good for weight loss?
It can be, if it helps you eat fewer calories overall. Weight loss results are similar to other diets with the same calorie intake.
How many calories should I eat during intermittent fasting?
The same as any diet: your TDEE minus a sensible deficit, usually around 500 calories. The window only changes when you eat it.
Will intermittent fasting make me lose muscle?
Not if you eat enough protein and strength train. Muscle loss depends mainly on total protein and the size of your deficit.