Calorie Deficit Calculator for Weight Loss
Use this calorie deficit calculator to discover how much weight is realistic for you to lose and the calories 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 are 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.
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.
What is a 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 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 eating 500 fewer calories a day, you will slowly lose 1 pound of weight a week. This amounts to 3,500 fewer calories a week (7 days times 500 calories) and is sometimes referred to as the 3,500 calories per pound rule. It is based on the fact that body fat contains approximately 3,500 calories of energy per pound.
Unfortunately, the rule does not take into account important contributing factors such as the physiological changes that occur during weight loss. 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. As you lose weight, so does your body's ability to burn calories.
Formulas incorporated into this online calculator are instead based on a mathematical model developed by Kevin Dennis Hall, Ph. D., and a team of researchers at the National Institute of Health. The formulas are much more accurate in determining energy expenditure and energy requirements for the purpose of weight management. They take into consideration the body dynamics and physiological changes that take place during weight loss.
To illustrate, if you are a 37 year old, 6 foot sedentary male weighing 265 pounds, your body burns around 2,600 calories a day and you need to intake that same amount of food energy to maintain your weight. Say you then go on a 1,600 calorie a day diet, a 1000 calorie deficit, to try and lose 85 pounds for a healthy BMI. You would be eating 7,000 less calories a week. According to the 3,500 calories per pound rule, you would lose (7000 / 3500) or 2 pounds a week and expect to lose 85 pounds after (85 / 2) or about 43 weeks. If we instead applied Hall’s mathematical model, it would show that it actually takes almost 70 weeks for that same weight loss.
Body weight loss through caloric restriction does not continue downwards indefinitely in a linear fashion as the 3,500 calories per pound rule would suggest. Rather, the loss levels off in a nonlinear fashion because of body dynamics. The actual weight loss curve is much more closely approximated by the Hall’s model.
How low of a calorie deficit should I go?
As a general rule, women should not eat less than 1,200 calories a day and men not less then 1,500 calories a day. Nutrition therapist will tell you that food group targets and nutrient recommendations will not be met below those levels.
Choosing a Healthy Goal Weight
Body fat percentage, not your weight, gives a far better picture of your overall health. An ideal goal weight would be one that puts you in a healthy body fat percentage category. You can use this calculator to help you determine what a healthy weight would be for you.
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.
- Calories: How to Know if You Go Too Low
- 6 Reasons Why You're Not Losing Weight In a Calorie Deficit
- Weight Loss Science, Calorie Deficit Paradox and The Biggest Loser
- 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.
- 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
- 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