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Intermittent Fasting Calculator

Online Intermittent Fasting Time Calculator



Intermittent fasting (IF) is an eating pattern where you cycle between periods of eating and fasting. It doesn’t prescribe specific foods to eat or avoid but instead focuses on when you should eat. IF has gained immense popularity over recent years due to its potential benefits for weight loss, metabolism, and even lifespan.

How to Use the Calculator:

  1. Choose Your Fasting Method: Select one of the four popular intermittent fasting schedules.
  2. Set Your Time: Choose whether you’d like to set the start or end time of your eating window.
  3. Calculate: Click the “Calculate” button to get your fasting and eating window.

Intermittent Fasting Spreadsheet

We also offer an Excel spreadsheet that you can download to your computer instead of the online calculator above.

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Intermittent Fasting Calculator

How to use this intermittent fasting calculator?

  • Select either the time you start eating or the time you stop eating.
  • Select the time you want to start or stop.
  • You will see the 18:6 intermittent fasting schedule (18:6 intermittent fasting is when you abstain from eating for 18 hours and eat all your meals in a 6-hour window).

Fasting Methods:

  1. 12/12: This method involves fasting for 12 hours and eating during a 12-hour window. It’s the most lenient form of IF and can be an excellent starting point for beginners.
  2. 16/8: Perhaps the most popular method, this involves fasting for 16 hours and eating during an 8-hour window. For instance, you might eat between 12 pm and 8 pm and fast from 8 pm to 12 pm the next day.
  3. 18/6: This is a slightly more extended fast, where you fast for 18 hours and eat during a 6-hour window. It’s slightly more challenging than the 16/8 method but can offer more pronounced benefits.
  4. 20/4: Known as the “Warrior Diet”, this method involves fasting for 20 hours and eating during a 4-hour window. It’s one of the more challenging forms of IF and is typically taken up by those well-adjusted to the fasting lifestyle.


  • Stay Hydrated: During your fasting periods, ensure you drink plenty of water. Herbal teas without sugar can also be consumed.
  • Stay Active: Engaging in light to moderate exercise can enhance the benefits of intermittent fasting. However, it’s vital to listen to your body.
  • Balanced Diet: During your eating window, focus on a balanced diet rich in proteins, whole grains, and vegetables. Aim for a mix of protein, healthy fats, and complex carbohydrates in each meal.
  • Listen to Your Body: If you feel unwell or find a particular method too challenging, consider trying a different fasting window or speaking with a healthcare professional.
  • Mindful Eating: Listen to your body’s hunger and fullness cues.
  • Avoid Overeating: While it might be tempting to eat larger portions after a fasting period, it’s essential to listen to your body’s signals and avoid overindulging. Overeating can counteract the benefits of intermittent fasting and lead to digestive discomfort.
  • Plan Ahead: Preparing balanced meals in advance can prevent grabbing unhealthy snacks out of sheer hunger.
  • Consume Fiber: Foods rich in fiber, such as whole grains, vegetables, and fruits, can help you feel full and satisfied, reducing the urge to overeat.
  • Eat Slowly: It takes time for your stomach to send signals to your brain that it’s full. Eating slowly can help you recognize these signals before you’ve eaten too much.

By adhering to these guidelines and being mindful of portion sizes, you can maximize the health benefits of intermittent fasting while enjoying delicious and nutritious meals during your eating window.


According to Healthline, intermittent fasting changes hormone levels and increases the release of the fat burning hormone norepinephrine (noradrenaline) to facilitate weight loss. However, the primary factor behind its effectiveness is that intermittent fasting naturally leads to reduced calorie consumption. However, if you overindulge and consume excessive amounts during your eating windows, it might negate any potential weight loss benefits. Healthline goes on to explain that intermittent fasting offers numerous advantages for both the body and mind. It can lead to weight reduction and potentially lower the chances of developing type 2 diabetes, heart ailments, and cancer. Additionally, it might contribute to increased longevity. Johns Hopkins added additional benefits such as boosting thinking and memory and improving physical performance.


Intermittent fasting is a flexible approach that can be adapted to fit into various lifestyles. The key is to find a balance that works for you, ensuring you maintain a nutritious diet during your eating window. Always consult with a healthcare professional before making significant changes to your diet or fasting routine.


The information provided in this article, including recommendations related to diet and intermittent fasting, is intended for informational purposes only. It is not meant to substitute for the advice provided by your own physician or other medical professionals. You should not use the information contained herein for diagnosing or treating a health problem or disease, or prescribing any medication. If you have or suspect that you have a medical problem, promptly contact your health care provider. Always consult with a healthcare professional before starting any new diet or exercise program.

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Photo of NicoleMy name is Nicole and I created this website to share the tools that keep me organized and productive and help me reach my goals. I hope that you will find them helpful too.

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