Intermittent Fasting Calculator

intermittent fasting

How do you calculate intermittent fasting?

To calculate intermittent fasting you should focus on your caloric intake and expenditure. Your ultimate goal should be to reduce your overall calorie consumption, not count the hours you're fasting...although it can be tempting early on in your journey.

Though its no exact science, here is how most people calculate intermittent fasting

  1. Determine your Basal Metabolic Rate (BMR):

    This is the amount of energy expended while at rest in a neutrally temperate environment. It can be calculated using the Harris-Benedict principle:

    For men: BMR = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) - (5.677 x age in years)

    For women: BMR = 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) - (4.330 x age in years)

    Note: You'll need to convert the weight to kg and height to cm if they're given in other units.

  2. Adjust BMR based on activity level:

    The BMR needs to be adjusted based on a person's activity level to get the Total Daily Energy Expenditure (TDEE).

    • Sedentary (little to no exercise): TDEE = BMR x 1.2
    • Lightly active (light exercise/sports 1-3 days/week): TDEE = BMR x 1.375
    • Moderately active (moderate exercise/sports 3-5 days/week): TDEE = BMR x 1.55
    • Very active (hard exercise/sports 6-7 days a week): TDEE = BMR x 1.725
    • Super active (very hard exercise/physical job & exercise 2x/day): TDEE = BMR x 1.9
  3. Determine the caloric intake for weight loss:

    Generally, creating a calorie deficit of 500 to 1000 calories a day can lead to a safe weight loss of about 0.5 to 1 kg a week. So, you'll subtract 500-1000 calories from your TDEE to get your caloric intake for weight loss.

  4. Apply intermittent fasting:

    Then, the individual applies an intermittent fasting approach to their eating schedule. Common methods include the 16/8 method (fast for 16 hours, eat during an 8-hour window), the 5:2 diet (eat normally for five days, then only consume 500-600 calories on two non-consecutive days), and Eat-Stop-Eat (a 24-hour fast once or twice a week).

DISCLAIMER: Always consult your doctor before beginning any kind of diet or exercise routine. All dietary programs carry a risk!

Use my calculator below to get the estimated date you'll achieve your weight loss goals, based on your activity level and anticipated weight loss per week. Feel free to use the Intermittent Fasting Weight Loss Chart for reference.

Fasting Method Description Potential Weight Loss per Week
16/8 Method Fasting every day for 14-16 hours and restricting the daily eating window to 8-10 hours. Within the eating window, 2-3 meals can be consumed. 0.5-1 kg
5:2 Diet Eating normally for 5 days of the week, while restricting calories to 500-600 on two non-consecutive days of the week. 0.5-1 kg
Eat-Stop-Eat A 24-hour fast once or twice a week. 0.5-1 kg
Alternate-Day Fasting Fasting every other day. On fasting days, some eat no food at all and others eat a very small amount, typically around 500 calories. 0.5-1 kg
The Warrior Diet Fasting during the day and eating a large meal at night. Eating small amounts of raw fruits and vegetables during the day, then eating one huge meal at night. 0.5-1 kg

Current Weight:
Weight Unit:
Target Weight:
Expected Loss Rate (per week in chosen weight unit):

Activity Level:


If you want to determine how many calories you need to cut to be at a caloric deficit daily, check out my calorie deficit calculator.

Matt Irving is the CEO of Super Easy Tech, LLC.
Matt is the founder of Make It Super Easy and creator of Super Easy CRM. He is a beast of a software engineer, blogger, and gamer. Feel free to connect on any of the platforms listed below.

Posted by: Matt Irving on 7/24/2023