Calorie Calculator
Calculate your daily calorie needs based on age, sex, weight, height, and activity level. See your BMR, maintenance calories, and targets for weight loss or gain.
This is the estimated calories to maintain your current weight.
Understanding Daily Calorie Needs: BMR, TDEE, and the Mifflin-St Jeor Equation
Understanding how many calories your body needs each day is one of the most fundamental aspects of nutrition and weight management. Whether your goal is to lose weight, maintain your current physique, or build muscle, knowing your daily calorie requirements provides a science-based foundation for making informed dietary decisions. This calculator uses the Mifflin-St Jeor equation, which is considered one of the most accurate methods for estimating calorie needs in healthy individuals.
What Is Basal Metabolic Rate (BMR)?
Basal Metabolic Rate, or BMR, represents the number of calories your body burns at complete rest to maintain essential life-sustaining functions. These functions include breathing, blood circulation, cell production, nutrient processing, and temperature regulation. Your BMR accounts for approximately 60 to 75 percent of your total daily calorie expenditure, making it the single largest component of your energy needs.
BMR is influenced by several factors, including body weight, height, age, and sex. Generally, individuals with more lean muscle mass have a higher BMR because muscle tissue is metabolically more active than fat tissue. This is why strength training can be an effective component of a weight management strategyโby increasing muscle mass, you can elevate your resting metabolic rate over time.
The Mifflin-St Jeor Equation
The Mifflin-St Jeor equation was developed in 1990 by Dr. Mark Mifflin and Dr. Sachiko St Jeor and has since been validated by numerous studies as one of the most reliable methods for estimating BMR. The American Dietetic Association recommends this equation as the preferred method for calculating resting metabolic rate in healthy, non-obese individuals.
The formula calculates BMR as follows: for men, BMR = (10 ร weight in kg) + (6.25 ร height in cm) โ (5 ร age in years) + 5. For women, the formula is identical except the constant changes to โ161 instead of +5. The equation takes into account the key physiological differences between sexes that affect metabolic rate, including differences in average body composition and hormonal profiles.
Understanding Total Daily Energy Expenditure (TDEE)
While BMR tells you how many calories your body needs at rest, Total Daily Energy Expenditure (TDEE) provides a more complete picture by factoring in your physical activity level. TDEE is calculated by multiplying your BMR by an activity factor that reflects your typical daily activity.
The activity multipliers range from 1.2 for sedentary individuals (little or no exercise, desk job) to 1.9 for extremely active individuals (intense exercise six to seven days per week or a physically demanding job). Most people fall somewhere in the moderate range (1.55), which corresponds to exercising three to five days per week. Your TDEE represents the total number of calories you need to consume to maintain your current weight.
Activity Levels Explained
Selecting the right activity level is crucial for accurate calorie estimation. Sedentary describes individuals who perform little to no exercise and primarily have desk-based work. Lightly active applies to those who engage in light exercise one to three days per week. Moderately active suits individuals who exercise at moderate intensity three to five days per week. Very active describes those who engage in hard exercise six to seven days per week. Extra active applies to athletes, individuals with physically demanding jobs, or those who train twice per day.
Be honest when selecting your activity level, as overestimating can lead to consuming more calories than you actually need. If you are unsure, it is generally better to select a slightly lower activity level and adjust based on your results over time.
Calorie Targets for Weight Management
A widely accepted principle in nutrition science is that a caloric deficit of approximately 500 calories per day leads to roughly one pound (0.45 kilograms) of weight loss per week, since one pound of body fat contains approximately 3,500 calories. Similarly, a surplus of 500 calories per day typically results in about one pound of weight gain per week.
However, these are general guidelines. Individual results vary based on factors such as metabolic adaptation, body composition, sleep quality, stress levels, and genetic predisposition. It is important not to set calorie intake too low, as extremely restrictive diets can lead to muscle loss, nutritional deficiencies, metabolic slowdown, and are difficult to sustain long-term. Most nutrition experts recommend not dropping below 1,200 calories per day for women or 1,500 for men without medical supervision.
Limitations and Considerations
While the Mifflin-St Jeor equation is one of the most accurate prediction equations available, it is still an estimate. Individual metabolic rates can vary by 10 to 15 percent from predicted values due to genetic factors, thyroid function, and other physiological variables. The equation may be less accurate for very muscular individuals, the elderly, or those with extreme body compositions.
For the most personalized approach, consider using this calculator as a starting point and then adjusting your intake based on real-world results. Track your weight and body composition over several weeks and modify your calorie target if you are not seeing the expected progress. Consulting with a registered dietitian or healthcare professional can provide additional guidance tailored to your specific health needs and goals.
Frequently Asked Questions
What is the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest just to maintain basic life functions like breathing and circulation. TDEE (Total Daily Energy Expenditure) includes your BMR plus all the calories burned through daily activities and exercise. TDEE is always higher than BMR and represents the total calories you need to maintain your current weight.
How accurate is the Mifflin-St Jeor equation?
The Mifflin-St Jeor equation is considered one of the most accurate BMR prediction equations, with studies showing it predicts actual resting metabolic rate within 10% for most healthy individuals. The American Dietetic Association recommends it as the preferred equation for estimating calorie needs. However, individual variation exists, so it is best used as a starting point and adjusted based on real-world results.
How many calories should I eat to lose weight?
A common approach is to eat 500 calories fewer than your TDEE per day, which typically results in about one pound (0.45 kg) of weight loss per week. This calculator shows this as the 'Weight Loss' target. However, avoid going below 1,200 calories per day for women or 1,500 for men without medical supervision, as very low calorie diets can cause muscle loss and nutritional deficiencies.
Does my calorie need change as I lose weight?
Yes. As you lose weight, your body requires fewer calories to maintain itself, so both your BMR and TDEE decrease. This is why weight loss often slows over time. It is recommended to recalculate your calorie needs every 5 to 10 pounds lost and adjust your intake accordingly to continue making progress.
Which activity level should I choose?
Choose the level that best matches your average week. Sedentary means little to no exercise and a desk job. Lightly active means light exercise 1 to 3 days per week. Moderately active means moderate exercise 3 to 5 days per week. Very active means hard exercise 6 to 7 days per week. Extra active is for athletes or those with very physically demanding jobs. When in doubt, select a slightly lower level, as people tend to overestimate their activity.