Daily calorie needs (TDEE)
Work out your resting metabolic rate with the Mifflin-St Jeor equation and your total daily energy expenditure at each of five activity levels, so you can see how much of the answer depends on the one thing you had to guess. The equation, its accuracy and its limits are published below.
Your figure at each activity level
| Sedentary | 1.2 | 1,644 |
| Lightly active | 1.375 | 1,884 |
| Moderately active | 1.55 | 2,124 |
| Very active | 1.725 | 2,364 |
| Extremely active | 1.9 | 2,603 |
An estimate, not medical advice. Body metrics are population averages and do not account for your individual circumstances. Speak to a clinician about anything that matters.
The same body at every rung of the ladder. Sedentary to extremely active is about 960 calories a day apart.
How it works
What this works out
Two numbers, and the gap between them. Your resting metabolic rate is what your body uses lying still and doing nothing: breathing, pumping blood, keeping tissue alive. Your total daily energy expenditure is that figure multiplied by how much you move, and it is the one to compare against what you eat.
Most people are surprised by how large the resting figure is relative to the total. For somebody with a desk job it is around five sixths of the whole day. Exercise moves the number less than the equation’s inputs — weight, height and age — do.
The method
The resting rate comes from Mifflin-St Jeor, published in 1990 from indirect calorimetry on 498 healthy adults. It replaced the Harris-Benedict equation of 1919 as the default because it was derived on a modern population, and a 2005 systematic review in the Journal of the American Dietetic Association found it estimated measured resting rate to within 10% more often than any other published equation. The two versions differ only in a constant: +5 for men, −161 for women, a gap of 166 calories for the same body. That constant is standing in for the average difference in lean mass, which is why the equation is least accurate at the extremes of body composition — it is reading weight, not muscle.
The total is the resting rate multiplied by an activity factor. This ladder — 1.2 through 1.9 in steps of 0.175 — is the conventional one rather than a figure from a primary source, and it should be treated as such. It is a practical stand-in for what the FAO/WHO/UNU consultation calls the physical activity level: the ratio of total energy expenditure to basal expenditure. Because the steps are equal, moving one rung always changes the answer by 0.175 of your resting rate, which is why the table below shows all five rather than only the one you chose. That table is the honest part of the page.
The calorie target for gaining or losing weight converts at 7,700 kcal per kilogram, so 0.5 kg a week is 550 calories a day. That rule comes from Wishnofsky in 1958 and it is the arithmetic behind the NHLBI’s advice that a deficit of 500 to 1,000 kcal a day produces a loss of one to two pounds a week. It is also known to be wrong over a longer horizon: Hall and colleagues showed in The Lancet in 2011 that the real long-run loss is roughly half what the rule predicts, because maintenance falls as you get lighter. The target is never displayed below 1,200 kcal for a woman or 1,500 for a man, which are the top of the ranges the NHLBI prescribes for a supervised low-calorie diet.
Before you read on
A 30-year-old woman, 165 cm, 65 kg. Between the bottom rung of the activity ladder and the top, how far does her daily calorie figure move?
959 calories a day — 1,644 at the bottom against 2,603 at the top, more than a third of the total. The Mifflin-St Jeor equation underneath is careful work derived on 498 adults by indirect calorimetry; the ladder multiplied over it is a convention rather than a figure from a primary source, and it is a description you picked off a list. That is the real precision of this answer, and it is why the whole table is on the page rather than only the row you chose.
- Resting rate (BMR)1,37064.5%
- Everything above resting75435.5%
A worked example
A 30-year-old woman, 165 cm, 65 kg, moderately active (three to five sessions a week).
BMR = 10 x 65 + 6.25 x 165 - 5 x 30 - 161
= 650 + 1031.25 - 150 - 161
= 1370.25 kcal/day
TDEE = 1370.25 x 1.55
= 2123.8875 kcal/day
| Calories to maintain your weight | 2,124 |
| Resting rate (BMR) | 1,370 |
| Everything above resting | 754 |
And the same body at every rung of the ladder:
| Activity level | Multiplier | Calories a day |
|---|---|---|
| Sedentary | 1.2 | 1,644 |
| Lightly active | 1.375 | 1,884 |
| Moderately active | 1.55 | 2,124 |
| Very active | 1.725 | 2,364 |
| Extremely active | 1.9 | 2,603 |
The spread from top to bottom is 959 calories a day — more than a third of the total, decided entirely by a description you picked from a list. That is the real precision of this answer, and it is the reason the whole table is on the page rather than just one row of it.
These are the same numbers asserted in this tool’s test file, so if the formula ever changes without this page changing with it, the build fails.
What it does not do
It does not measure anything. It predicts a population average from four inputs, and the review that recommends it is explicit that noteworthy errors remain for individuals. It ignores body composition, so a muscular person is underestimated and someone carrying more fat at the same weight is overestimated. It has nothing to say about pregnancy, breastfeeding, thyroid conditions or medication that changes metabolic rate, and it is not intended for anyone under 18. If you need a figure you can rely on clinically, the measurement is indirect calorimetry and this is not it.
It says nothing about where your weight sits against your height, which is a different measure with a different set of limits. A BMI calculator answers that one, and its own page is honest about how little it settles.
The formula
Mifflin-St Jeor (1990), resting metabolic rate in kcal per day:
men BMR = 10 x weight + 6.25 x height - 5 x age + 5
women BMR = 10 x weight + 6.25 x height - 5 x age - 161
where
weight = kilograms
height = centimetres
age = years
Total daily energy expenditure:
TDEE = BMR x activity multiplier
1.200 sedentary
1.375 lightly active
1.550 moderately active
1.725 very active
1.900 extremely active
Calorie target for a chosen rate of weight change:
target = TDEE + (kg per week x 7700 / 7)
floored at 1200 kcal (women) and 1500 kcal (men)
What it assumes
- The equation predicts a group average rather than you. Frankenfield's systematic review found it the most reliable of the equations tested, estimating resting rate to within 10% of a measured value more often than any other, while noting that errors and limitations remain.
- The activity multiplier is a self-assessment and it is the largest source of error here. Each rung of the ladder is 0.175 of your resting rate away from the next, which is about 240 calories a day for the worked example below.
- Body composition is ignored. The equation takes total body weight, so it tends to underestimate a muscular person and overestimate somebody carrying more fat at the same weight.
- Weight change is converted at 7,700 kcal per kilogram. That holds for a few weeks and then overstates the loss, because maintenance falls as you get lighter.
- The calorie target is never displayed below 1,200 kcal for women or 1,500 for men. Those are the top of the range the NHLBI's 1998 clinical guidance prescribes for a low-calorie diet, used here as a floor.
- Nothing here accounts for pregnancy, breastfeeding, a thyroid condition, or medication that changes metabolic rate. It is not intended for anyone under 18.
- Calorie means kilocalorie throughout, which is what a food label in Britain prints as kcal and an American one prints as Calories.
Common questions
Why does every calorie calculator give me a different number?
Two reasons. Some use a different resting-rate equation — Harris-Benedict from 1919, Katch-McArdle if you have supplied a body fat figure — and those differ from Mifflin-St Jeor by 50 to 150 calories for a typical adult. The larger reason is the activity multiplier, which is a self-assessment: one rung of the ladder is worth about 240 calories a day, so two honest people describing the same week can land 500 apart.
What is the difference between BMR and TDEE?
BMR is what your body uses at complete rest — breathing, circulation, keeping your organs running — and it is typically 60 to 70% of the total. TDEE adds everything else: walking about, deliberate exercise, and the energy cost of digesting food. TDEE is the figure to compare against what you eat.
Which activity level should I pick?
Pick the lower of the two you are torn between. The ladder describes your whole week rather than your best week, and the multiplier already includes ordinary daily movement, so a desk job with three gym sessions is lightly to moderately active, not very active. Getting this wrong in the optimistic direction is the single most common reason a calorie target does not work.
Is Mifflin-St Jeor better than Harris-Benedict?
For most adults, yes. Frankenfield's 2005 systematic review compared the published equations against measured resting rates and found Mifflin-St Jeor landed within 10% of the measurement more often than any other, which is why it became the default in dietetic practice. It still carries noteworthy errors and limitations, and the review says so in as many words.
Why is there no option other than female and male?
Because the paper published two constants and no third one exists to use. Adding an average of the two would be inventing a figure and presenting it as a measurement. If neither fits, the honest reading is to run it both ways and treat the 166-calorie gap between them as the uncertainty.
Are my height, weight and age sent anywhere?
No. The arithmetic runs in this browser tab and there is no server to send it to. Your height, weight and age never leave the device, which is the reason this page has no account and asks for no email.
Sources
- A new predictive equation for resting energy expenditure in healthy individuals
- Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review
- Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults: Treatment Guidelines
- Quantification of the effect of energy imbalance on bodyweight
- Human energy requirements. Report of a Joint FAO/WHO/UNU Expert Consultation