Intermittent Fasting Calculator

Plan your intermittent fasting schedule with 6 protocols (16:8, 18:6, 20:4, OMAD, 5:2, ADF), eating window visualization, and macro targets. Free, fast, and private — runs entirely in your browser.

Fasting Protocol

Biological Sex

Current Weight (kg)

Goal Weight (kg, optional)

Height (cm)

Age (years)

Activity Level

Preferred Eating Window Start Time

:(12:00 PM)

Your Daily Schedule

16h Fast

8h Eat

Fasting Window

8:00 PM - 12:00 PM

16 hours

Eating Window

12:00 PM - 8:00 PM

8 hours

What You Can Have During Fasting

✓

Water

Plain, sparkling, or with lemon

✓

Black Coffee

No sugar, cream, or milk

✓

Plain Tea

Green, black, or herbal (unsweetened)

✓

Apple Cider Vinegar

1-2 tbsp diluted in water

✓

Bone Broth

Light broth for electrolytes (may break strict fast)

✗

Anything with Calories

Juice, milk, sweeteners break your fast

Hydration Reminder

Aim for at least 2-3 liters (8-12 glasses) of water per day during intermittent fasting. Staying hydrated helps manage hunger, supports metabolism, and prevents headaches. Increase intake on active or hot days.

Enter your weight, height, and age above to calculate your personalized intermittent fasting plan.

Disclaimer

This calculator provides estimates based on the Mifflin-St Jeor equation and standard activity multipliers. Individual results may vary significantly based on metabolism, genetics, body composition, and adherence.

This is not medical advice. Intermittent fasting is not suitable for everyone, including pregnant or breastfeeding women, children, people with eating disorders, type 1 diabetes, or those on certain medications. Always consult a healthcare professional before starting any fasting regimen.

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How to Use Intermittent Fasting Calculator

1Select your fasting protocol (16:8, 18:6, etc.).
2Set your preferred eating window start time.
3Enter your stats for calorie and macro calculations.
4View your daily schedule and nutrition targets.

Frequently Asked Questions

What is intermittent fasting?▾

Intermittent fasting (IF) is an eating pattern that cycles between periods of fasting and eating. Popular methods include 16:8, 18:6, and OMAD.

Which IF protocol is best for beginners?▾

16:8 is the most popular starting point — fast for 16 hours and eat during an 8-hour window. It's sustainable and easy to follow.

Is this calculator free?▾

Yes, completely free with no sign-up required. All calculations run in your browser.

Does it calculate calories and macros?▾

Yes, the calculator provides calorie targets and macro breakdowns based on your goals (fat loss, maintenance, or muscle gain).

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About Intermittent Fasting Calculator

Plan your intermittent fasting schedule with 6 protocols (16:8, 18:6, 20:4, OMAD, 5:2, ADF), eating window visualization, and macro targets. Free, fast, and private — runs entirely in your browser.

NexTool's Intermittent Fasting Calculator is completely free to use with no sign-up required. Your data is processed directly in your browser and never sent to our servers, ensuring complete privacy and instant results.