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Intermittent Fasting Window Calculator

Work out intermittent fasting window instantly with clear inputs, formula shown and shareable results.

About Intermittent Fasting Window Calculator

Splits the 24-hour day into the chosen eating window and the resulting fast, and spaces the meals across the window.

Formula

Time-restricted eating

Fasting hours = 24 - eating window; window closes at first meal time + window length

Worked example

With the default values below, Intermittent Fasting Window Calculator returns Daily fasting hours of 16.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Eating windowaccepts 1–16 h
8 h
Hour of the first mealaccepts 0–23
12
Meals in the windowaccepts 1–6
2

Results

Daily fasting hours
16.00 h
Eating window closes at
20:00
Fasting hours per week
112.0 h
Hours between meals
8.00 h

Step by step

  1. 1Values used
  2. 2Time-restricted eating
  3. 3Daily fasting hours= 16.00 h
  4. 4Eating window closes at= 20:00
  5. 5Fasting hours per week= 112.0 h
  6. 6Hours between meals= 8.00 h

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
  • This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

Frequently Asked Questions

Which schedule is most studied?

16:8 time-restricted eating is the most common, with early time-restricted eating showing the strongest metabolic signals.

Does the window position matter?

Evidence favours an earlier window aligned with daylight over late-evening eating.

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