TDEE Calculator: Total Daily Energy Expenditure

TDEE Calculator

Total daily energy expenditure (TDEE) is the amount of energy a body uses over a whole day, counting rest, digestion, daily movement and exercise. This TDEE calculator estimates that figure in kilocalories per day (kcal/day) from sex, age, height, weight and a chosen activity level.

What the calculator does

The calculator takes a unit system (metric or imperial), sex, age in years, height, weight, and one of five activity levels. It returns four things:

• TDEE in kcal/day for the level chosen.
• The basal metabolic rate (BMR) the TDEE was built from.
• TDEE at all five activity levels, so the effect of the choice is visible.
• Both formula lines with the entered numbers written into them.

Imperial input is converted before the equation runs. Height in feet and inches becomes centimetres, and pounds become kilograms.

The TDEE formula

TDEE is calculated in two steps.

Step 1. Basal metabolic rate. BMR is the energy a body uses at rest, doing nothing but staying alive. The calculator uses the Mifflin-St Jeor equation, published by Mifflin, St Jeor, Hill, Scott, Daugherty and Koh in the American Journal of Clinical Nutrition in 1990:

Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) + 5

Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) − 161

The two constants, +5 and −161, are the only difference between the published versions.

Step 2. Multiply by an activity level.

TDEE = BMR × PAL

PAL stands for physical activity level. It is the ratio of total daily energy use to basal energy use. A PAL of 1.5 means a body uses half again as much energy over a day as it would lying still. This relation is defined in the FAO/WHO/UNU report Human energy requirements (Rome 2001, published 2004), chapter 5.

Activity multipliers

The calculator offers five fixed PAL values. They are the tabulated ladder from McArdle, Katch and Katch, Exercise Physiology: Nutrition, Energy, and Human Performance.

Example: metric

A man aged 30, 175 cm tall, weighing 70 kg, moderately active.

BMR = 10 × 70 + 6.25 × 175 − 5 × 30 + 5 BMR = 700 + 1093.75 − 150 + 5 = 1648.75 kcal/day, shown as 1649.

TDEE = 1648.75 × 1.55 = 2555.5625, shown as 2556 kcal/day.

The same BMR at every rung of the ladder:

The gap between the lowest and highest rung is 1154 kcal/day, about 58 percent of the sedentary figure. The activity choice moves the answer more than anything else on the form.

Example: imperial

A woman aged 40, 5 feet 9 in tall, weighing 154 lb, lightly active.

First the units are converted. Height: (5 × 12 + 9) inches = 69 inches, and 69 × 2.54 = 175.26 cm. Weight: 154 × 0.45359237 = 69.85 kg. These factors are the exact 1959 international definitions of the inch and the pound.

BMR = 10 × 69.85 + 6.25 × 175.26 − 5 × 40 − 161 BMR = 698.53 + 1095.375 − 200 − 161 = 1432.91 kcal/day, shown as 1433.

TDEE = 1432.91 × 1.375 = 1970.25, shown as 1970 kcal/day.

Displayed values are rounded to whole kilocalories, while the arithmetic runs on the unrounded numbers. Redoing a line by hand can therefore differ by one in the last digit.

How the ladder compares with the FAO/WHO/UNU bands

The five multipliers are not the FAO/WHO/UNU lifestyle bands, and they do not sit inside them. Chapter 5 of that report (table 5.3) groups lifestyles as sedentary or light at PAL 1.40 to 1.69, active at 1.70 to 1.99, and vigorous at 2.00 to 2.40.

Two rungs of the ladder, 1.2 and 1.375, fall below the FAO sedentary floor of 1.40. The top rung, 1.9, falls below the vigorous band. So the ladder is narrower than the bands at both ends. Multiplying the same BMR by 1.40 instead of 1.2 raises the result by about 17 percent.

The report also declines to go below 1.40. It reviews the 1985 figure of 1.21 for totally inactive dependent people, judges it too low even for emergency relief, and recommends 1.40 in its place.

Limits of the estimate

The result is a population estimate, not a measurement of one person's metabolism.

• The equation was fitted on adults. The study population was 498 healthy adults aged 19 to 78. The equation was not validated for children, adolescents, pregnancy, or adults older than that range. The calculator flags an age outside 19 to 78.
• Accuracy. A systematic review found the equation predicted measured resting metabolic rate to within 10 percent for about 82 percent of adults who were not obese and about 70 percent of adults who were obese. Individual error can exceed 20 percent.
• It estimates RMR, not strictly BMR. The 1990 study measured resting metabolic rate, taken under resting rather than strictly basal conditions. The common label BMR is used here, but the quantity is RMR.
• Body composition is not an input. The equation uses total body weight, not lean mass. It tends to read high for people carrying a high proportion of body fat and low for very muscular people of the same weight.
• The multipliers are conventions. They are round numbers from a table, not measurements. Doubly-labelled-water studies of real people put PAL anywhere from about 1.2 to 2.5 (Black and colleagues, 1996).
• Self-rating is the weakest link. Choosing one's own activity level is a coarse judgement, and it is usually the largest source of error in the whole estimate.

The calculator computes and states definitions. It does not recommend an intake, a deficit, a surplus, or any course of action.

Frequently asked questions

What is the difference between BMR and TDEE? BMR is the energy a body uses at rest. TDEE is the energy it uses over a whole day, including movement and exercise. TDEE is BMR multiplied by an activity level, so it is always the larger of the two.

Which formula does this calculator use? Mifflin-St Jeor (1990) for the BMR, then TDEE = BMR × PAL as defined by FAO/WHO/UNU. The PAL values come from the five-step ladder tabulated by McArdle, Katch and Katch.

Why does the answer change so much when the activity level changes? The multiplier is applied to the whole BMR. Moving from 1.2 to 1.9 is a 58 percent increase in the result. In the metric example above that is a difference of 1154 kcal/day from one menu choice.

Are the multipliers the same as the FAO/WHO/UNU bands? No. The FAO bands start at 1.40 and reach 2.40. The ladder runs from 1.2 to 1.9, so it goes lower at the bottom and stops short at the top.

How accurate is the number? It is within 10 percent of measured resting metabolic rate for roughly 82 percent of non-obese adults and 70 percent of obese adults, before any error from the activity multiplier is added. Only indirect calorimetry or a doubly-labelled-water study measures a person's actual expenditure.

Does it work for children or during pregnancy? The equation was not fitted or validated for either group, so the result has no established accuracy there.

Sources

• Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247.
• FAO/WHO/UNU. Human energy requirements. Report of a Joint FAO/WHO/UNU Expert Consultation, Rome 2001. FAO Food and Nutrition Technical Report Series No. 1, 2004, chapter 5.
• McArdle WD, Katch FI, Katch VL. Exercise Physiology: Nutrition, Energy, and Human Performance. Lippincott Williams & Wilkins.
• Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc. 2005;105(5):775-789.
• Black AE, Coward WA, Cole TJ, Prentice AM. Human energy expenditure in affluent societies: an analysis of 574 doubly-labelled water measurements. Eur J Clin Nutr. 1996;50(2):72-92.