— Intermittent Fasting Calculator
Find Your Eating Window in Seconds
Select your fasting protocol, enter your last meal time, and get your exact fasting and eating window — with science-backed recommendations for your goal.
1 — Choose Your Fasting Protocol
2 — Enter Your Details
— Your Fasting Schedule
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Fasting Starts (last meal)
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Eating Window Opens
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Eating Window Closes
16h
Fasting Window
8h
Eating Window
16:8
Protocol
— Recommendation for Your Goal
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⚠️ Medical Disclaimer: This tool is for educational purposes only. If you have diabetes, are pregnant or breastfeeding, take glucose-lowering medication (insulin, metformin, GLP-1 agonists), have a history of eating disorders, or have any chronic medical condition — consult a qualified healthcare professional before beginning any fasting protocol.
— Protocol Guide
Which Fasting Protocol Is Right for You?
Choose based on your lifestyle, training schedule, and goal — not what's trending.
12:12
The Foundation
The natural overnight fast most people already do. A good starting point before moving to longer protocols. Minimal disruption to social eating.
14:10
The Step Up
A gentle extension of the overnight fast. Effective for appetite control without significant lifestyle disruption. Ideal for people with early-morning training.
16:8
The Gold Standard
The most researched protocol. Skipping breakfast and eating from midday to 8pm. Clinically shown to reduce calorie intake and improve insulin sensitivity.
18:6
The Serious Protocol
An 18-hour fast with a 6-hour eating window. Requires fitting all meals between e.g. 12:00–18:00. Effective for fat loss but can conflict with evening social eating.
20:4
The Warrior Diet
A 20-hour fast with a 4-hour eating window. Originally called the Warrior Diet. Requires consuming all daily calories in a very tight window — challenging but effective.
OMAD
One Meal a Day
A 23-hour fast with a 1-hour eating window. Extreme protocol requiring careful planning to hit protein and micronutrient targets. Not recommended for most people.
— Fasting Support
Products That Support Your Fasting Protocol
Zero-calorie products that don't break your fast and help maintain energy, hydration, and focus during the fasting window. Affiliate links — we earn a commission at no cost to you.
Electrolytes
Zero-Calorie Electrolyte Mixes
Electrolytes are depleted faster during fasting. A zero-calorie electrolyte mix prevents fasting headaches, fatigue, and muscle cramps without breaking your fast.
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Appetite Control
Quality Black Coffee & Green Tea
Caffeine suppresses ghrelin (the hunger hormone) and enhances fat oxidation during fasted states. Black coffee and plain green tea do not break a fast.
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Breaking the Fast
High-Protein First Meal Options
Breaking your fast with protein and fibre — not carbohydrates — prevents the blood sugar spike and subsequent hunger crash that can derail the rest of your eating window.
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— Research Basis
The Science Behind This Calculator
This tool is built on the following peer-reviewed research.
Study 01
Intermittent Fasting and Human Metabolic Health — de Cabo & Mattson, 2019
New England Journal of Medicine — IF improves insulin sensitivity, blood lipids, and body composition across multiple protocols. PubMed ↗
Study 02
Effect of 16:8 Time-Restricted Eating on Body Weight — Lowe et al., 2020
JAMA Internal Medicine — 12-week RCT showing 16:8 reduced calorie intake and body weight without calorie counting. PubMed ↗
Study 03
Time-Restricted Eating and Muscle Mass — Tinsley & La Bounty, 2015
Nutrition Reviews — Adequate protein intake within the eating window preserves muscle mass during IF protocols. PubMed ↗