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Intermittent Fasting Calculator

Plan your fasting and eating windows (16:8, 18:6, OMAD…) from your last meal time.

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Open Intermittent Fasting Calculator and you get an answer straight away, with no account to create. It covers 16:8, 18:6, OMAD — adjust any of them and the result follows immediately.

How to use it

  1. Open the tool — no signup or install needed.
  2. Enter your input or adjust the available options.
  3. Get your result instantly, then copy or download it.

Frequently asked questions

What does Intermittent Fasting Calculator do?

Plan your fasting and eating windows (16:8, 18:6, OMAD…) from your last meal time.

What does it take into account?

It factors in 16:8, 18:6, OMAD. Change any of them and the output follows immediately.

When would I actually use this?

Planning meals against a target, checking whether a habit covers the recommended intake, and translating a label into what it means for the day.

What is the most common mistake?

Treating a daily target as a daily requirement. Reference intakes are population averages over time; a day above or below one means nothing on its own.

Is there a tool for the next step?

Breastfeeding Calorie Calculator is the closest one after this: Extra daily calories while breastfeeding — about +500 kcal exclusive, with a gradual weight-loss option.

What else is worth having open alongside it?

Carb-to-Insulin Ratio Calculator and Carbohydrate Calculator — they come up in the same task often enough to be worth a second tab.

Where do the figures come from?

Reference intakes come from public health bodies (EFSA in Europe, the NIH and USDA in the United States) and differ between them. They describe populations, not you, and are not medical advice.

Further reading

All guides →
Comparison16/8, 5:2 or Alternate Day: The Fasting Protocols ComparedFive protocols side by side, what each demands, and the uncomfortable finding from the controlled trials: matched for calories, fasting loses about the same weight as simply eating less.How-toHow to Calculate Keto Macros (Without Starting From the Percentages)Set carbs as a fixed gram figure, protein by body weight, and let fat fill what is left. The famous 75 percent fat is an output of that calculation, not an input — and it drops on its own in a deficit.ExplainerHow Much Fiber Per Day Do You Need?Daily fiber targets of 25 to 38 grams by sex and age, why fiber matters for digestion and heart health, and the best food sources to hit your goal.ExplainerHow Much Sodium Per Day Is Safe?The 2,300 mg FDA limit, the 1,500 mg ideal from the AHA, and why most sodium is hidden in packaged food — plus how to read labels and cut back.ExplainerHow Much Sugar Per Day Is Healthy?The WHO limit on free sugars, how to turn a percentage of calories into grams, and where hidden sugar comes from — with practical daily targets.ExplainerWhat Breastfeeding Actually Costs in Energy — and Why the Published Number Is Smaller Than the MilkMilk production has a computable cost: volume times energy density divided by the efficiency of conversion. Do the sum and you get about 675 kcal a day, not the 500 that gets quoted. Here is the derivation, why the published increment is deliberately lower, how much the real spread is between mothers, what the water requirement actually rests on, and why cutting calories while feeding is a clinical question.