Nutrition & Cooking

Intermittent Fasting Calculator (16:8 and Other Schedules)

Pick a fasting schedule and your first meal time to see your eating window.

By TheCalcTools Updated October 17, 2026 Formula checked and tested

Your numbers

Schedule

First meal hour (0-23)

First meal minutes

Your results

Eating window

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Hours of eating

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Hours of fasting

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Fasting hours per week

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Intermittent Fasting Calculator (16:8 and Other Schedules) by TheCalcTools

How the Intermittent Fasting Calculator (16:8 and Other Schedules) works

Time-restricted eating confines all meals to a daily window and fasts for the rest of the 24 hours. With 16:8 and a first meal at noon, you eat from 12:00 to 8:00 PM and fast until noon the next day.

Water, black coffee and plain tea are usually allowed while fasting. Intermittent fasting is not suitable for everyone, including people with diabetes on certain medicines, during pregnancy or with a history of eating disorders.

The formula

Window end = first meal + (24 − fasting hours)

Worked example

Using the default values shown in the calculator:

Schedule	16:8
First meal hour (0-23)	12
First meal minutes	0

16:8 starting at noon: eat 12:00 PM to 8:00 PM, then fast 16 hours.

Result:

Eating window	12:00 PM to 8:00 PM
Hours of eating	8
Hours of fasting	16
Fasting hours per week	112

Frequently asked questions

Does intermittent fasting work better than calorie counting?

Trials generally find similar weight loss when total calories are matched; some people simply find a time window easier to follow.

Sources and further reading

More in Nutrition & Cooking · All calculators

This calculator gives general estimates for information and education. It is not medical advice and does not diagnose anything. Talk to a qualified health professional about your own situation. See our disclaimer.