TDEE Calculator for All Ages

Calculate your TDEE with this calculator to determine the number of calories your body burns in a day. It's accurate for all ages, including infants and toddlers. The calculator uses formulas developed by the Institute of Medicine of the National Academies, published in their Dietary Reference Intakes (DRI) report.

What is TDEE?

Total Daily Energy Expenditure (TDEE) is the total calories your body burns in a day to support its metabolic processes and physical activities. It's also the amount you need to consume to maintain your current weight. Eating less than your TDEE will lead to weight loss while consuming more than your TDEE will result in weight gain.

Your body constantly burns energy to support its autonomic systems, such as breathing, the nervous system, circulation, body temperature regulation, and physical activities. Energy is also required to transport, synthesize and replace molecules that makeup body tissue. The body releases chemical bonds in the foods you eat through oxidization to get the needed energy.

The three macronutrients that supply your body with energy from food are carbohydrates, protein, and fat. When oxidized, carbohydrates and proteins release about 4 kcal of energy per gram, while fat releases about 9 kcal per gram.

Your Body's Energy Expenditure Components

BMR (Basal Metabolic Rate)

Basal metabolic rate (BMR) is your body's energy expenditure rate when digestion of food and physical activity has minimal influence on your metabolism. It reflects the minimum energy needed to sustain metabolic processes that keep you alive. An accurate BMR measurement requires a specific setting, such as an overnight fast where the subject hasn't eaten for 12 to 14 hours, resting awake and motionless while lying on their back in a thermoneutral environment. To be more meaningful, BMR is usually extrapolated over 24 hours, referred to as basal energy expenditure (BEE), and expressed as kcal per day.

The tools needed to measure BMR are not always readily accessible. However, BMR and BEE can be estimated using prediction equations derived from body parameters such as weight, height, sex, and age. BMR is related to body size and is most closely correlated with lean body mass, which is total body weight minus the weight of its fat mass. Studies show that lean body mass significantly impacts BMR and accounts for about 73 percent of your BMR. Fat mass accounts for only an additional 2 percent.

TEF (Thermic Effect of Food)

TEF is the energy required to digest, absorb, transport, metabolize, and store ingested nutrients. It accounts for a percentage of the body's total energy expenditure and depends on the amount and composition of the consumed food. Fats require the least energy to be processed, carbs are next in line, and protein requires the most. Consuming an average mixture of macros will elicit an additional energy expenditure equivalent to about 10 percent of the consumed energy content.

TEPA (Thermic Effect of Physical Activity)

The energy expended from physical activity is the most variable component of your body's energy expenditure. It varies significantly among individuals. The Thermic Effect of Physical Activity typically accounts for 15 to 30% of daily calorie burn. It can rise to as much as 50% or more in active individuals, heavy laborers, and athletes. TEPA includes the energy expended through structured exercises and non-exercise activity thermogenesis (NEAT). NEAT refers to the energy burned through typical daily living activities such as performing household tasks, walking to the bus, light activities while sitting, driving, shopping, and fidgeting.

TDEE and Weight Management

TDEE is the sum of basal energy expenditure (BEE), the expenditure due to food's thermic effect (TEF), and the thermic effect of physical activity (TEPA). TDEE also includes energy expenditures for infants and children due to new tissue growth.

Your body will maintain its current weight if the number of calories you consume and digest equals the number of calories you expend (your TDEE). Consume more than your TDEE, and you will gain weight because the surplus calories get stored as fat in fat tissues. Consume less than your TDEE, and you will lose weight because your body will break down stored fat to get the extra energy it needs.

Energy Expenditure Measurements and Calculations

Numerous online calculators can estimate TDEE. They typically use prediction formulas first to estimate BMR, resting metabolic rate (RMR), or resting energy expenditure (REE). They then multiply that estimate by a factor corresponding to your level of physical activity to arrive at a TDEE value.

These prediction formulas often estimate an individual's BMR, RMR, or REE based on height, weight, sex, and age. The revised Harris-Benedict equation, the Mifflin St-Jeor equation, and the Katch-McArdle formulas are some of the more popular ones. Their formulas were developed using data on energy expenditure gathered from individuals in the general population. These data are usually collected through indirect calorimetry measurements conducted in controlled laboratory environments. Indirect calorimetry involves measuring an individual's oxygen consumption (oxygen uptake) and carbon dioxide production (carbon dioxide output) to estimate the amount of energy expended.

This calculator, instead, uses the most recent predictive formulas developed by the Institute of Medicine of the National Academies. Their formulas were derived from energy expenditure data from Doubly Labelled Water (DWL) studies. DLW is a superior energy expenditure measurement method because it applies to individuals under free-living conditions and real-life scenarios. It has become the gold standard methodology in determining TDEE. The method involves administering two stable isotopic forms of water to a subject and measuring their disappearance rates from body fluid (urine or blood) over 1- to 3 weeks. The differences in their disappearance rate reflect the amount of carbon dioxide production. From the disappearance rate and with knowledge of the diet composition, TDEE can be accurately determined.

Direct measurement of TDEE by the DLW method represents a distinct advantage over previous TDEE evaluation methods. The development of the DRI formulas for predicting TDEE was based on an analysis of TDEE measurements made on individuals obtained by the DLW method. Measurements were made on 767 adults ages 19 and over, 844 children ages 3 through 18, and 320 infants and children up to 2 years of age.

Estimated Energy Requirement (EER)

The Dietary Reference Intakes report defines Estimated Energy Requirement (EER) as the calorie intake required to maintain long-term good health. Therefore, this calculator expresses energy expenditure in terms of EER instead of TDEE for normal-weight individuals. The EER prediction formulas apply to:

1. Adults with a BMI (Body Mass Index) from 18.5 to 25.
2. Children ages 3 through 18 within the 5th to 85th percentile for BMI.
3. Infants and very young children, 0 through 2 years of age, within the 3rd to 97th percentile for BMI.

Overweight individuals who desire to lose weight can, instead, refer to their TDEE value, estimated by this calculator using the DRI formulas. It can be used as a baseline in planning an appropriate weight loss goal. To achieve a desirable lower steady-state body weight, overweight individuals must intake fewer calories than their current TDEE. Consuming 200 fewer calories daily than their TDEE would be a good starting point. TDEE decreases with weight loss, so TDEE should be checked regularly throughout your weight loss journey to ensure calorie intakes remain below TDEE.

The calculator applies different TDEE and EER formulas depending on the subject's age, sex, and weight status. The formulas accept age in years, weight in kilograms (kg), and height in meters (m).

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