This intermittent fasting calculator helps you plan your fasting schedule. Whether you’re following a 16:8, 18:6, or any other fasting schedule, this tool helps you determine your ideal eating and fasting windows based on your goals and daily routine. Simply enter your details, and the calculator will generate calorie and protein breakdown per meal that matches with your desired fasting schedule. Whether you’re aiming for weight loss, building muscle, or just feeling better, this tool will help you stay on track.
Also check out other related nutrition calculators on this site, including the macronutrient percentage calculator, protein calculator for weight loss, meat protein grams calculator, and net carb calculator.
Intermittent Fasting Protein & Calorie Calculator
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What Is intermittent fasting?
Intermittent fasting (IF) is an eating pattern that alternates between periods of eating and fasting. Unlike traditional diets that focus on what to eat, IF emphasises when to eat. The most common methods include the 16:8 approach (16 hours of fasting, 8 hours of eating), the 5:2 diet (eating normally for five days and significantly reducing calories for two), and OMAD (one meal a day). During fasting periods, the body shifts from burning glucose to using stored fat for energy, which can support weight loss, improve metabolism, and enhance overall health.
Intermittent fasting frequently asked questions
Here are some general FAQs to get your started:
What is intermittent fasting?
Intermittent fasting is an eating pattern that alternates between periods of eating and fasting, focusing on when you eat rather than what you eat, and works by cycling between eating and fasting periods, allowing the body to use stored fat for energy instead of glucose.
How long has IF been around?
Fasting has been practiced for centuries for religious, cultural, and health reasons, but scientific research on its health benefits gained momentum in the early 2000s, leading to its current widespread adoption.
What should I have during the fasting period?
Stick to zero-calorie options like water, black coffee, tea, and electrolytes to stay hydrated and support fasting benefits.
Does IF have any benefits?
Systematic reviews and meta analyses have shown that intermittent fasting can have beneficial effects on a range of health outcomes for adults who are overweight or obese. Specifically, intermittent fasting may decrease waist circumference, fat mass, LDL cholesterol, triglycerides, total cholesterol, fasting insulin, and systolic blood pressure, while beneficially increasing HDL cholesterol and fat free mass (i.e., muscle). It has also been shown to enhance brain function and potentially increase longevity. However, results vary from person to person.
How many hours is considered IF?
Any fasting period of 12 hours or more is generally considered intermittent fasting, with common methods ranging from 12 to 24 hours.
How long is the eating window while fasting?
The eating window depends on the fasting method and can range from 4 to 10 hours, depending on your chosen schedule. For example, a 16:8 schedule has an 8-hour eating window, while an 18:6 schedule allows for 6 hours.
Do overnight hours count?
Yes. Sleeping hours count toward your fasting period, making it easier to complete longer fasts without feeling hungry.
How to calculate fasting hours?
Count the total hours between your last meal of the day and your first meal the next day. For example, if you eat at 8 PM and again at 12 PM, that’s a 16-hour fast.
Do you have to fast every day for it to work?
No, but consistency helps. Many people fast daily, while others do it a few times per week.
You can also fast on select days, such as alternate-day fasting or the 5:2 method, where you eat normally for five days and reduce calories on two days.
Can I skip a day? What will happen?
Yes. Nothing will happen from skipping a day, and it won’t ruin your progress. Just get back on track the next day.
Does IF work?
Not for everyone. Success depends on factors like diet, consistency, metabolism, and overall lifestyle.
How long will IF take to work?
Some people notice changes in a few days to a week, but most people start seeing results within 2 to 4 weeks and can vary based on diet, activity, and metabolism.
How many months can you fast?
You can practice intermittent fasting indefinitely, as long as you maintain proper nutrition and balance.
What is the best IF schedule?
It depends on your lifestyle, goals, and what’s tolerable for you. 16:8 is the most popular, but 18:6, 20:4, and OMAD (one meal a day) work well for some.
Does intermittent fasting work quickly for weight loss?
Some people see changes within a few weeks, especially if paired with a healthy diet.
How much weight can you lose in a month on intermittent fasting?
Weight loss depends on caloric intake and activity level, but many people lose 4–10 pounds (2–5 kg) per month. It depends on factors like diet, metabolism, and consistency, but steady weight loss is common over time.
Can intermittent fasting cause anxiety?
For some, fasting may temporarily increase anxiety, especially if blood sugar drops or stress levels are high. Staying hydrated and eating balanced meals can help.
Can IF be bad for me or cause problems?
Intermittent fasting is generally safe for most people, but it may not be suitable for those with certain medical conditions, a history of eating disorders, or those who are pregnant or underweight. If done improperly, it can cause problems such as fatigue, headaches, dizziness, or nutrient deficiencies.
What should I have during the fasting period?
Stick to zero-calorie options like water, black coffee, tea, and electrolytes to stay hydrated and support fasting benefits.
How does intermittent fasting affect calorie intake?
Intermittent fasting naturally reduces calorie intake by limiting your eating window, but weight loss still depends on what and how much you eat during eating periods.