Intermittent Fasting Calculator

Build your fasting schedule in seconds. Choose a plan (16:8, 18:6, 20:4, OMAD) or create a custom window. This calculator returns your fasting start, eating window, next meal time, and a screenshot-friendly plan you can share.

⚡Instant fasting & eating windows

🧠Works for 16:8, 18:6, 20:4, OMAD

📱Perfect for screenshots & sharing

✅Simple, realistic guidance

Choose your fasting plan

Pick a fasting style and tell us when you want your eating window to start (or when you last ate). We’ll generate a clean daily schedule you can follow consistently.

Fasting plan

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Schedule anchor

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Time

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Custom fast (hours)

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Custom eat (hours)

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Your fasting schedule will appear here

Choose a plan and press “Build My Fasting Schedule”.

Tip: Consistency matters more than perfection. Build a plan you can repeat.

This calculator provides general information, not medical advice. If you’re pregnant, under 18, have a history of eating disorders, diabetes, or take medications affected by meal timing, consult a clinician before fasting.

🎯What you get

Fast + eat window, instantly

You’ll receive a daily fasting plan with clear start/end times and an eating window you can follow consistently.

Fasting start & fasting end times
Eating window (start → end)
Next meal time you can aim for
Simple tips that make fasting easier

Pro tip: The “best” fasting plan is the one you can repeat 5–6 days/week without misery.

🔥Viral fasting tips

Make it easier (and more shareable)

If you want a plan that actually sticks, simplify your window and automate your food choices.

Pick a consistent eating window (ex: 12–8pm).
Keep protein high at your first meal.
Use sparkling water + electrolytes if needed.
Don’t turn fasting into “starve all day, binge at night”.

📚 Explanation

What intermittent fasting is

Intermittent fasting (IF) is an eating schedule that alternates between periods of eating and periods of fasting. The key idea is not “magic fat burning,” but structure. Many people find IF helpful because it reduces decision fatigue and naturally shortens the time window where they eat, which can make calorie control easier.

The 3 most common fasting styles

16:8: Fast 16 hours, eat within an 8-hour window (most popular).
18:6: A slightly tighter eating window for people who want more structure.
20:4 / OMAD: Short windows that can work for some, but require planning to avoid under-eating protein.

What this calculator actually does

Turns your plan (fasting hours + eating hours) into exact clock times.
Lets you anchor the plan to eating start or last meal end.
Outputs a schedule that’s easy to screenshot and follow daily.

🧮 Formula

Fasting window math

The math is simple time arithmetic. Each day is 24 hours. Most IF plans are written as fasting hours : eating hours, and those two numbers always add to 24.

Core relationship

FastHours + EatHours = 24
FastEnd = FastStart + FastHours
EatEnd = EatStart + EatHours

Anchors explained

If you anchor to Eat Start: we set EatStart = your chosen time, then EatEnd, then FastStart = EatEnd.
If you anchor to Last Meal End: we set FastStart = your chosen time, then FastEnd, then EatStart = FastEnd.

✅ Practical guide

How to use intermittent fasting for real life results

The biggest mistake people make is thinking IF is automatically fat loss. It’s not. IF is a schedule. Results still come from total calorie intake, protein, training, and sleep. Here’s how to make your fasting window work:

1) Keep protein high

In most diets, protein is the macronutrient most tied to muscle retention and satiety. If you fast longer but eat low protein, you can end up hungry and lose lean mass over time. Aim to distribute protein across your eating window, especially your first meal.

2) Start with the easiest plan

For most people, 16:8 is the best starting point. It’s flexible, social-life friendly, and can be built around lunch/dinner. If you try OMAD immediately, you may under-eat protein or binge in one sitting.

3) Pick an eating window you can repeat

Consistency beats “perfect.” A plan you can repeat 5–6 days/week is better than a strict plan you do for 3 days and quit. Common windows: 12–8pm, 11–7pm, 1–9pm.

4) Hydration & electrolytes matter

Many “fasting headaches” are dehydration or sodium issues. Water, sparkling water, and electrolytes can help. If you’re exercising while fasting, electrolyte support becomes more important.

🧪 Examples

Example fasting schedules

Here are a few common setups. You can replicate them in the calculator for your timezone and preference.

Example 1: 16:8 with lunch start

Eat Start: 12:00pm
Eat End: 8:00pm
Fast Start: 8:00pm
Fast End (next day): 12:00pm

Example 2: 18:6 with earlier dinner

Eat Start: 11:00am
Eat End: 5:00pm
Fast Start: 5:00pm
Fast End (next day): 11:00am

Example 3: OMAD anchor to last meal end

Last meal ends: 7:00pm
Fast Start: 7:00pm
Fast End: 6:00pm next day (23 hours)
Eat Window: 6:00–7:00pm

❓ FAQ

Frequently Asked Questions

Is intermittent fasting safe?
For many healthy adults it can be, but it’s not ideal for everyone. If you’re pregnant, under 18, have diabetes, a history of eating disorders, or take medications influenced by meal timing, check with a clinician first.
Does coffee break a fast?
Black coffee typically has minimal calories and is commonly used during fasting. Add-ins like sugar, cream, or flavored syrups can break a fast depending on goals.
What if I train in the morning?
You can still fast. Some people train fasted and eat later; others shift the eating window earlier. Choose the setup that supports training performance and recovery.
Will IF automatically make me lose weight?
No. IF can make calorie control easier by reducing eating opportunities, but total intake and food quality still matter.
What’s the best plan for beginners?
Usually 16:8. It’s flexible, sustainable, and easy to build around lunch and dinner.
How long does it take to adapt?
Many people adapt in 7–14 days. Start with a gentle window and focus on hydration, protein, and sleep.

🧠 Quick tips

Make fasting work without misery

Plan your first meal so you don’t break the fast with random snacks.
Protein first: prioritize protein and fiber to stay full.
Keep electrolytes in mind, especially if you feel headaches.
Sleep matters: poor sleep increases hunger signals.
Consistency wins: repeatable beats extreme.

MaximCalculator provides simple tools for education and planning. Always treat fasting and nutrition results as general guidance, and consult qualified professionals for medical decisions.