Resting Energy Expenditure Calculator
Resting Energy Expenditure (REE) is the calories your body burns at rest. The Mifflin-St Jeor equation (1990) is the most accurate predictive formula, recommended by the Academy of Nutrition and Dietetics (AND). It requires weight, height, age, and sex. The result is in kilocalories per day. This calculator also estimates Total Daily Energy Expenditure (TDEE) based on your activity level.
Mifflin-St Jeor equation (1990)
Men: REE = (10 x weight_kg) + (6.25 x height_cm) - (5 x age_years) + 5
Women: REE = (10 x weight_kg) + (6.25 x height_cm) - (5 x age_years) - 161
TDEE = REE x Activity Factor
Source: Mifflin MD, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247. PMID 2305711. The equation has a standard error of approximately 5% when compared to indirect calorimetry.
Activity factor reference
- Sedentary (desk job, little walking): 1.2
- Lightly active (exercise 1-3 days per week): 1.375
- Moderately active (exercise 3-5 days per week): 1.55
- Very active (hard exercise 6-7 days per week): 1.725
- Extra active (very hard exercise plus physical job): 1.9
Resting energy expenditure calculator: frequently asked questions
What is Resting Energy Expenditure?
Resting Energy Expenditure (REE), also called Resting Metabolic Rate (RMR), is the amount of energy the body expends at rest to maintain basic physiological functions such as breathing, circulation, temperature regulation, and organ function. It accounts for approximately 60-75% of Total Daily Energy Expenditure (TDEE) in sedentary individuals. REE differs slightly from Basal Metabolic Rate (BMR), which is measured under strict fasting and resting conditions.
What is the Mifflin-St Jeor equation?
The Mifflin-St Jeor equation (1990): For men: REE = (10 x weight_kg) + (6.25 x height_cm) - (5 x age) + 5. For women: REE = (10 x weight_kg) + (6.25 x height_cm) - (5 x age) - 161. It was derived from a controlled study of 498 healthy adults and has been found to be the most accurate predictive equation for REE compared to measured indirect calorimetry, with a mean error of approximately 5%. It is recommended by the Academy of Nutrition and Dietetics (AND) and the American Dietetic Association (ADA).
How does REE differ from BMR?
BMR (Basal Metabolic Rate) is measured in a thermoneutral environment, in a supine position, after a 12-hour fast and 8 hours of sleep, in a completely relaxed state. REE (Resting Energy Expenditure) is measured after only a brief rest period (30 minutes) and a shorter fast (4-6 hours), making it more practical for clinical measurement. REE is typically about 10% higher than true BMR due to the less strict measurement conditions.
How accurate are predictive equations for REE?
The Mifflin-St Jeor equation is the most accurate commonly used predictive equation, with a mean error of approximately 5% compared to indirect calorimetry measured REE. Other equations (Harris-Benedict, Owen, WHO) have larger mean errors. In obese individuals, all equations tend to be less accurate, and the Mifflin-St Jeor equation is still the preferred option. For the most accurate REE, direct measurement by indirect calorimetry is required.
How do I use REE to plan calorie intake?
To estimate Total Daily Energy Expenditure (TDEE), multiply REE by an activity factor: 1.2 (sedentary), 1.375 (light activity), 1.55 (moderate activity), 1.725 (very active), or 1.9 (extra active). To lose weight, aim for a caloric deficit of 500-1,000 kcal/day below TDEE. To gain muscle mass, aim for a surplus of 250-500 kcal/day. These estimates should be adjusted based on actual weight change over 2-4 weeks.
Official sources
- Mifflin MD, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247. Available via PubMed 2305711.
- Academy of Nutrition and Dietetics Evidence Analysis Library: Energy Expenditure and Requirements.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.