Calorie Deficit Calculator for Weight Loss

Use this calculator to discover how much weight is realistic for you to lose and the calorie deficit needed to achieve that weight loss. Enter your body details and a goal weight. The calculator will then generate a table and a graph showing daily calorie intakes and estimated times to reach your goal weight.

Calorie intakes will be shown in descending units of 50 calories. For each unit decrease, you can see how much sooner it would take to reach your goal weight. You can then choose a calorie intake level that you think is doable and try to stick to it for that period of time.

Calorie Deficit Calculator


Enter your body parameters, activity level and a goal weight. If you don't know your activity level, click the Estimate button. It will pop up a form where you can make a selection from activities at work and from activities during leisure times. An activity level value will be generated for you based on your selections.

Consult a doctor for guidance and support if you are considering a diet of less than 1,000 Calories (4200 kJ) per day. As a general rule, you should not eat less than 1200 calories a day. Nutrition therapist will tell you that food group targets and nutrient recommendations will not be met below that level.

What is calorie deficit?

A calorie deficit is created when you intake less food energy than your body requires. In that state, your body draws on your fat stores to burn the extra energy it needs, resulting in weight loss.

You need energy to support your body’s autonomic systems such as breathing, digestion, the nervous system, circulation and regulation of body temperature. Energy is also required in performing daily physical activities. The more physical activities performed, such as through work or exercise, the more energy your body requires.

Through a combination of increased physical activity and reduction in energy intake, a calorie deficit will be ensured.

How do you calculate a calorie deficit?

Your calorie deficit is the energy your body requires to survive and maintain your current weight, minus your dietary calorie intake. So for example, if your body requires 2,000 calories a day and you only feed it 1,200 calories a day, you are in a 800 calorie deficit.

Do you lose a pound a week with a 500 calorie deficit?

It is a myth that by being in a calorie deficit of 500 calories a day, you will slowly lose 1 lb of weight a week. This is sometimes referred to as the 3,500 calories per pound rule. It does not take into account important contributing factors such as the physiological changes that occur during weight loss, your sex, age and initial weight. The amounts of body fat and muscle tissue both change with an energy imbalance. When you reduce your energy intake, muscle mass is lost along with fat mass. Considering that muscle burns more energy than fat, as you lose weight, so does your body's ability to burn calories.

Formulas incorporated into this calculator are instead based on a model developed by Kevin Hall, Ph. D., and a team of researchers at the National Institute of Health. It is much more accurate in determining energy expenditure and energy requirements for the purpose of weight management. It takes into consideration the physiological changes that take place during weight loss along with all the other relevant factors.

As an example, if you are in a 500 calorie a day deficit, you would lose about 1 lb a week according to the rule. So if you were planning on losing say 25 lbs, it would take you (25 x 1) or 25 weeks to do so.

This is clearly wrong and you would be disappointed. According to the Hall's model, it would actually take over 37 weeks if you were a 34 year old, 6 foot sedentary male initially weighing 250 lbs. Actual times would vary depending on sex, age, height and initial weight.

Total Energy Expenditure and Resting Metabolic Rate

Your Total Daily Energy Expenditure (TDEE) and Resting Metabolic Rate (RMR) are also calculated.

TDEE (total daily energy expenditure) is the total amount of energy your body burns daily and is equivalent to the amount needed to maintain your current body weight. Eat less than that amount and you will lose weight. Your RMR (resting metabolic rate) is the amount of energy your body burns while at rest. RMR is factored into TDEE.

Body Fat Percentage

The calculator also calculates your body fat percentage based on your BMI (Body Mass Index). It uses regression equations published in a paper by Jackson et al. Although not as accurate as other popular body fat measurement methods, it nonetheless gives a ball park estimate for the purposes of weight loss calculations.

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Related Articles


  1. Quantification of the effect of energy imbalance on bodyweight.
    Hall KD, Sacks G, Chandramohan D, Chow CC, Wang YC, Gortmaker SL, Swinburn BA.
    Lancet (2011 Aug 27) 27;378(9793):826-37.
  2. The effect of sex, age and race on estimating percentage body fat from body mass index.
    Jackson et al.
    International Journal of Obesity (2002) 26, 789–796
  3. A new predictive equation for resting energy expenditure in healthy individuals.
    M D Mifflin, S T St Jeor, L A Hill, B J Scott, S A Daugherty, Y O Koh
    The American Journal of Clinical Nutrition, Volume 51, Issue 2, February 1990, Pages 241–247

Last Update: Jan 17, 2021 12:30 EST