Calorie Calculator: Daily Calorie Target from TDEE

What is a calorie calculator?

A calorie calculator estimates how much food energy a person uses in a day, then adjusts that figure for a chosen rate of weight change. This tool works out three numbers: the basal metabolic rate (BMR), the total daily energy expenditure (TDEE), and a daily calorie target. The rate of weight change is entered by the user. The tool converts that rate into energy; it does not suggest a rate, a deficit, or an intake level.

The "calories" counted on food labels are kilocalories (kcal). One kilocalorie is the energy that raises the temperature of one kilogram of water by one degree Celsius, and equals 4.184 kilojoules exactly.

Calorie formula

The calculation runs in three steps.

Step 1: basal metabolic rate. BMR is the energy a body uses at rest, before any activity is added. This tool uses the Mifflin-St Jeor equation, published by Mifflin and colleagues in the American Journal of Clinical Nutrition in 1990. Weight is in kilograms, height in centimetres, age in years, and the result is kcal per day.

$BMR_{men} = 10w + 6.25h - 5a + 5$

$BMR_{women} = 10w + 6.25h - 5a - 161$

The two coefficient sets differ only in the last constant, +5 or −161.

Step 2: total daily energy expenditure. TDEE is BMR multiplied by a physical activity level (PAL), the ratio of total energy use to resting energy use. The relation TDEE = BMR × PAL comes from the FAO/WHO/UNU report Human Energy Requirements (Rome 2001, published 2004), chapter 5.

$TDEE = BMR \times PAL$

Step 3: the weight-change adjustment. A weekly rate of weight change is turned into a daily energy difference using the energy equivalent of body tissue published by Max Wishnofsky in 1958: 3,500 kcal per pound of body weight. The metric constant this tool uses, 7,700 kcal per kilogram, is the rounded restatement of that figure.

$\text{daily adjustment} = \frac{\text{weekly change} \times \text{kcal per unit}}{7}$

$\text{target} = TDEE + \text{daily adjustment}$

The weekly rate is signed. Zero means the target equals TDEE. A negative rate lowers the target, and a positive rate raises it.

Activity multipliers

The tool offers five fixed multipliers, the ladder tabulated in McArdle, Katch and Katch's Exercise Physiology.

These five steps are conventions, not measurements. They are also not the FAO/WHO/UNU bands, which run from 1.40 to 1.69 for a sedentary or light lifestyle, 1.70 to 1.99 for an active one, and 2.00 to 2.40 for a vigorous one. Two of the five steps, 1.2 and 1.375, sit below the FAO sedentary floor of 1.40, and the top step of 1.9 sits below the vigorous band. Using 1.40 in place of 1.2 raises the result by about 17 percent, and the daily target moves with it kcal for kcal.

How to calculate a daily calorie target

Metric example. A man aged 30, 175 cm tall, weighing 70 kg, moderately active, with a chosen rate of −0.5 kg per week.

$BMR = 10(70) + 6.25(175) - 5(30) + 5 = 1{,}648.75$

$TDEE = 1{,}648.75 \times 1.55 = 2{,}555.56$

$\text{daily adjustment} = \frac{-0.5 \times 7{,}700}{7} = -550$

$\text{target} = 2{,}555.56 - 550 = 2{,}005.56$

The tool displays 1,649 kcal/day for BMR, 2,556 kcal/day for TDEE, −550 kcal/day for the adjustment, and 2,006 kcal/day for the target. The weekly energy difference is −0.5 × 7,700 = −3,850 kcal per week.

Imperial example. A woman aged 35, 5 feet 4 inches tall, weighing 150 lb, lightly active, with a chosen rate of −1 lb per week. Height and weight are converted first, because the equation takes centimetres and kilograms: 64 in × 2.54 = 162.56 cm, and 150 lb × 0.45359237 = 68.04 kg.

$BMR = 10(68.04) + 6.25(162.56) - 5(35) - 161 = 1{,}360.39$

$TDEE = 1{,}360.39 \times 1.375 = 1{,}870.53$

$\text{daily adjustment} = \frac{-1 \times 3{,}500}{7} = -500$

$\text{target} = 1{,}870.53 - 500 = 1{,}370.53$

The tool displays 1,360 kcal/day for BMR, 1,871 kcal/day for TDEE, and 1,371 kcal/day for the target.

Displayed figures are rounded to whole kilocalories, and the height and weight printed in the formula lines are rounded to two decimals. The arithmetic runs on the unrounded values, so a line redone by hand can differ by one in the last digit.

Limits of the estimate

Each of the three steps carries its own error, and they stack.

• The BMR equation is a population fit. Mifflin-St Jeor was fitted on 498 healthy adults aged 19 to 78. It was not validated for children, for adolescents, during pregnancy, or for adults older than that range. A 2005 systematic review by Frankenfield and colleagues found it 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 pass 20 percent.
• It uses total body weight, not lean mass. Muscle burns more energy at rest than fat does, so the equation tends to read high for people carrying a high proportion of body fat and low for very muscular people of the same weight.
• It estimates resting metabolic rate, not strictly basal rate. The 1990 study measured people at rest rather than under the stricter basal conditions the label BMR implies. The tool uses the common label BMR, but the equation estimates resting metabolic rate.
• The activity multiplier is usually the largest source of error. Doubly labelled water studies, which track energy use in free-living people, put real activity levels anywhere from about 1.2 to 2.5. A person picking their own band from a short description is guessing at a number the whole result is multiplied by.
• The 3,500 kcal rule is a static approximation from 1958. Dynamic models, such as the one published by Hall and colleagues in The Lancet in 2011, show that actual weight change per unit of energy imbalance is smaller than the rule predicts and shrinks over time as the body adapts.
• The two unit systems differ slightly. Converting 3,500 kcal per pound exactly gives 7,716 kcal per kilogram, not 7,700. The same physical rate therefore lands about 0.2 percent apart in metric and imperial.

Frequently asked questions

What is the difference between BMR and TDEE?

BMR is the energy a body uses at rest, with no activity. TDEE is BMR multiplied by an activity level, so it covers everything a person does in a day. TDEE is always the larger number.

Why does the target equal TDEE when the weekly rate is zero?

The adjustment term is the weekly rate multiplied by the energy constant and divided by 7. A rate of zero makes that term zero, so the target is TDEE unchanged.

Is a calorie the same as a kilocalorie?

On food labels, yes. The "Calorie" written on packaging is a kilocalorie, or 1,000 small calories. This tool reports kilocalories (kcal) throughout.

Why do two calculators give different numbers for the same person?

Most differences come from the BMR equation and the activity ladder. Harris-Benedict, Mifflin-St Jeor, Katch-McArdle and Cunningham all produce different BMR values, and activity ladders vary between sites. Multiplying the same BMR by 1.2 rather than 1.55 changes the result by about 29 percent.

Does the calculator account for body fat percentage?

No. Mifflin-St Jeor takes only weight, height, age and sex. Equations such as Katch-McArdle use lean body mass instead, which requires a body-composition measurement.

Can the calculator return a target below zero?

The arithmetic allows it, if the weekly rate entered is large enough relative to TDEE. The tool shows the value and marks it as a result no food intake can meet.

References

• 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.
• Wishnofsky M. Caloric equivalents of gained or lost weight. Am J Clin Nutr. 1958;6(5):542-546.
• 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.
• Hall KD, Sacks G, Chandramohan D, Chow CC, Wang YC, Gortmaker SL, Swinburn BA. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011;378(9793):826-837.