Water Fasting Calculator

What Is the Water Fasting Calculator?

The Water Fasting Calculator is a free online tool designed to help you estimate how much weight you might lose during a water fast. Whether you're planning a short 24-hour fast or a longer multi-day water fast, this tool uses your personal details—like age, gender, height, weight, activity level, and fasting duration—to give you clear and personalized predictions.

What Does the Calculator Do?

The Water Fasting Calculator estimates the following:

• Basal Metabolic Rate (BMR) - the number of calories your body burns at rest.
• Total Daily Energy Expenditure (TDEE) - your BMR plus calories burned from daily activity.
• Total Caloric Deficit - the number of calories you'll "miss" during your fast.
• Estimated Fat Loss - how much fat your body may burn to meet energy needs.
• Water and Glycogen Loss - early weight loss from depleted glycogen stores and water.
• Total Estimated Weight Loss - a sum of fat, glycogen, and water loss.
• Your Estimated Weight After Fasting - a projected post-fast weight.

Key Features

✅ Easy to Use Inputs

The calculator asks for simple inputs like:

• Age
• Gender
• Height (in feet/inches or centimeters)
• Weight (in pounds or kilograms)
• Activity level (from sedentary to extra active)
• Fasting duration (days and hours)

✅ Real-Time Results

After clicking the “Calculate” button, you instantly see a breakdown of your fasting results without needing to sign up or download anything.

✅ Free and No Sign-Up Required

Our calculator is completely free to use. You don't need to create an account or provide any personal information. Just enter your details and get your results instantly.

How to use the Water Fasting Calculator

To use the Water Fasting Calculator, simply follow these steps:

1. Enter your age, gender, height, and current weight.
2. Select your activity level — from sedentary to very active.
3. Input your fasting duration in days and/or hours.
4. Click the “Calculate” button to see your estimated weight loss, calorie deficit, fat loss, and final weight.
5. Optional: Click “🖨️ Print Report” to save or print your results.

Example: What You'll See After Using the Calculator

Note: These are estimates and actual results may vary based on individual factors.

How Does the Calculator Work

The calculator estimates your weight loss by using your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) to determine how many calories you burn while fasting.

It then applies standard formulas to calculate fat loss (based on the calorie deficit), water loss (from glycogen depletion), and your final weight after the fast.

The calculations rely on science-backed estimates, such as 1 pound of fat equaling roughly 3,500 calories.

What is Water Fasting?

Water fasting is a method of fasting that involves consuming water instead of food. This method is often used to help people lose weight and improve their health. Water fasting is a low-calorie diet that is easy to follow and can help you reach your weight loss goals. It is also a great way to maintain a healthy lifestyle and improve your overall well-being.

Benefits of Water Fasting

Water fasting has many benefits, including:

• Reducing the risk of weight gain
• Improving blood sugar levels
• Improving digestion
• Reducing inflammation
• Improving overall health

How to Start Water Fasting

To start water fasting, you need to first determine your basal metabolic rate (BMR) and total daily energy expenditure (TDEE). Once you have these values, you can calculate the total caloric deficit and the estimated fat loss. You can then use this information to determine the amount of water and glycogen you need to consume to reach your weight loss goals.

Frequently Asked Questions

What is a Water Fasting Calculator?

The Water Fasting Calculator is a free tool that estimates your weight loss during a water fast. It calculates fat loss, calorie deficit, water loss, and your final weight after the fast.

How does the calculator estimate weight loss?

It uses your BMR and TDEE to estimate how many calories you burn during fasting. Then it calculates fat and water loss based on standard formulas (1 pound of fat ≈ 3,500 calories).

Can I trust the weight loss results?

The results are estimates based on science-backed formulas. However, actual results may vary. Always consult a healthcare provider before prolonged fasting.

Is this calculator free?

✅ Yes! 100% free with no sign-up or installation required.

What inputs do I need?

Input Field	Description
Age	Your age in years
Gender	Male or Female
Height	In ft/in or cm
Weight	In lbs or kg
Activity Level	Sedentary to very active
Fasting Duration	Days and/or hours

What is BMR?

BMR (Basal Metabolic Rate) is the number of calories your body burns at rest. It's used to estimate your energy needs and fasting weight loss.

What is TDEE?

TDEE (Total Daily Energy Expenditure) includes your BMR plus calories burned from activity. It's the total energy you use daily.

What are glycogen and water losses?

During fasting, glycogen stores are used up along with water stored in your body, leading to quick initial weight loss.

How accurate are these results?

They are good estimates but may vary depending on health, metabolism, hormones, and lifestyle factors.

Is it safe to do long water fasts?

Prolonged fasting should be done under medical supervision, especially for people with health conditions or on medications.

Do I enter both days and hours?

You can enter either or both. Example: 0 days and 16 hours for a short fast, or 3 days and 0 hours for a multi-day fast.

Can I print the fasting results?

✅ Yes! Use the “🖨️ Print Report” button to print or save your results as a PDF.

Who created this calculator?

This calculator is developed by Khem Raj and Team, focused on building accurate and helpful health calculators for public use.