Use this calculator to estimate your potential weight loss journey with intermittent fasting. It helps you understand the calorie deficit needed and the estimated time to reach your target weight based on your personal metrics and activity level.
Male
Female
Sedentary (little to no exercise)
Lightly Active (light exercise/sports 1-3 days/week)
Moderately Active (moderate exercise/sports 3-5 days/week)
Very Active (hard exercise/sports 6-7 days/week)
Extra Active (very hard exercise/physical job)
Recommended safe weight loss is 0.5 to 2 lbs per week.
Understanding Intermittent Fasting for Weight Loss
Intermittent fasting (IF) is an eating pattern that cycles between periods of eating and voluntary fasting. It doesn't dictate *what* you eat, but *when* you eat. Popular methods include the 16/8 method (fasting for 16 hours and eating within an 8-hour window), the 5:2 method (eating normally for five days and restricting calories to 500-600 on two non-consecutive days), and Eat-Stop-Eat (24-hour fasts once or twice a week).
How Intermittent Fasting Aids Weight Loss
The primary mechanism by which intermittent fasting leads to weight loss is by naturally reducing your overall calorie intake. By shortening your eating window or having dedicated low-calorie days, it often becomes easier to consume fewer calories than your body burns, creating the necessary calorie deficit for fat loss.
Calorie Restriction: The most direct way IF helps is by making it simpler to eat less. Skipping a meal, like breakfast, can significantly cut down on daily calories.
Metabolic Changes: Fasting can lead to several beneficial metabolic changes. It can lower insulin levels, which helps the body access stored body fat for energy. It also increases levels of human growth hormone (HGH), which can aid fat loss and muscle gain.
Improved Insulin Sensitivity: Lower insulin levels and improved insulin sensitivity can make your body more efficient at burning fat.
The Role of Calorie Deficit
Regardless of the diet method, weight loss fundamentally comes down to consuming fewer calories than your body expends. This is known as a calorie deficit. Approximately 3,500 calories equate to one pound of body fat. Therefore, to lose one pound of fat per week, you need to create a daily deficit of about 500 calories (3500 calories / 7 days).
Our calculator helps you determine your Basal Metabolic Rate (BMR) – the calories your body burns at rest – and your Total Daily Energy Expenditure (TDEE) – the total calories you burn including activity. By knowing your TDEE, you can then calculate the daily calorie intake required to achieve your desired weekly weight loss.
Using the Intermittent Fasting Weight Loss Calculator
To get the most accurate estimate, provide your current weight, target weight, height, age, gender, and an honest assessment of your activity level. The "Desired Weekly Weight Loss" field allows you to set a realistic goal, typically between 0.5 to 2 pounds per week for sustainable and healthy weight loss.
Current Weight & Target Weight: These define the total amount of weight you aim to lose.
Height, Age, Gender: These factors are crucial for calculating your BMR using the Mifflin-St Jeor equation, a widely accepted formula.
Activity Level: This adjusts your BMR to your TDEE, accounting for the calories you burn through daily activities and exercise.
Desired Weekly Weight Loss: This input directly influences the daily calorie deficit the calculator will recommend.
Important Considerations for Intermittent Fasting
Nutrient Density: During your eating windows, focus on consuming nutrient-dense foods: lean proteins, healthy fats, plenty of fruits and vegetables, and whole grains. This ensures you get all essential nutrients despite eating less frequently.
Hydration: Drink plenty of water, unsweetened tea, or black coffee during your fasting periods to stay hydrated and help manage hunger.
Listen to Your Body: Intermittent fasting is not for everyone. If you experience extreme hunger, fatigue, or other adverse effects, it may not be the right approach for you, or you may need to adjust your fasting schedule.
Consult a Professional: Always consult with a doctor or a registered dietitian before starting any new diet regimen, especially if you have underlying health conditions, are pregnant, breastfeeding, or taking medications.
This calculator provides an estimate to guide your journey. Consistency, proper nutrition, and listening to your body are key to successful and sustainable weight loss with intermittent fasting.