Mifflin-St Jeor Equation

On this page

1. The equation
2. Where it came from
3. How to calculate it step by step
4. More examples
5. What each part of the equation means
6. How accurate is it?
7. From Mifflin-St Jeor to TDEE
8. Using it to plan weight loss
9. What happens with age
10. How it compares with other equations
11. Recalculating as your weight changes
12. Mifflin-St Jeor equation questions

The equation

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

In US units, with the conversions built in:

Men: BMR = 4.536 × weight (lb) + 15.875 × height (in) − 5 × age + 5 Women: BMR = 4.536 × weight (lb) + 15.875 × height (in) − 5 × age − 161

The result is in kilocalories (kcal) a day: the energy your body would use lying completely still.

Where it came from

By the 1980s, the main equation in use was Harris-Benedict, built in 1918 from a small group of mostly young, lean adults. Clinicians had noticed that it often overestimated the needs of people living modern lives. In 1990, Mark Mifflin, Sachiko St Jeor and colleagues published a new equation in the American Journal of Clinical Nutrition, based on resting metabolism measured in 498 healthy men and women aged 19 to 78, including people with obesity.

They found that weight, height and age explained most of the differences between people, with a separate constant for men and women. The result was simpler than Harris-Benedict and, in later comparisons, more accurate. In 2005, a systematic review for the American Dietetic Association recommended it as the equation most likely to predict resting metabolism within 10% in healthy adults, with and without obesity.

How to calculate it step by step

Take a 41-year-old woman, 170 cm (5′7″) and 68 kg (150 lb):

1. Weight part: 10 × 68 = 680
2. Height part: 6.25 × 170 = 1,062.5
3. Age part: 5 × 41 = 205
4. Put it together: 680 + 1,062.5 − 205 − 161 = 1,377 kcal

And a 28-year-old man, 6′0″ (72 in) and 170 lb, using the US version:

1. Weight part: 4.536 × 170 = 771.1
2. Height part: 15.875 × 72 = 1,143
3. Age part: 5 × 28 = 140
4. Put it together: 771.1 + 1,143 − 140 + 5 = 1,779 kcal

More examples

Sedentary is BMR × 1.2; moderately active is BMR × 1.55. The BMR calculator does all of this instantly and compares it with three other equations.

What each part of the equation means

• 10 × weight: every kilo of you costs about 10 kcal a day to keep running. Bigger bodies have more tissue to maintain.
• 6.25 × height: taller people of the same weight tend to have more lean mass and larger organs, so they burn more.
• − 5 × age: resting metabolism tends to fall slightly with age, about 50 kcal per decade in this equation, mostly reflecting less muscle.
• + 5 or − 161: at the same size, men average more lean mass than women, which the equation captures as a 166 kcal difference.

Notice what is missing: body fat. The equation can’t tell a muscular 90 kg person from a 90 kg person with more fat. That is its main weakness.

How accurate is it?

For healthy adults, Mifflin-St Jeor is the most reliable of the common equations, predicting within about 10% of measured resting metabolism for most people. That still leaves room for error: some individuals sit 15 to 20% away from the prediction. The groups most likely to be off are:

• Lean, muscular people, whom it tends to underestimate. Katch-McArdle or Cunningham, which use lean mass, often fit better.
• Older adults with little muscle, whom it may overestimate.
• Some non-European populations. Studies in some Asian and tropical populations found that standard equations can overestimate resting energy.
• People with thyroid disease or other conditions, and people taking medicines that change metabolism.

It is also not designed for children and teenagers, or for pregnancy and breastfeeding.

From Mifflin-St Jeor to TDEE

The equation gives your resting burn. To estimate your total daily burn, multiply by an activity factor:

The jump between levels is far bigger than any error in the equation itself, so choose your level carefully. When in doubt, take the lower one. Our TDEE calculator uses Mifflin-St Jeor by default and shows your TDEE at every level.

Using it to plan weight loss

Back to the 41-year-old woman, 170 cm and 68 kg. She teaches, walks a fair amount and does yoga once a week, so she chooses lightly active.

BMR = 1,377 kcal TDEE = 1,377 × 1.375 = 1,893 kcal Target = 1,893 × 0.8 = 1,514 kcal a day (a deficit of about 380 kcal) Pace = about 0.34 kg (¾ lb) a week at first

If she reaches 62 kg (137 lb), her BMR falls to 1,317 kcal and her TDEE to about 1,810. The same 1,514 kcal is then only a 16% deficit, so her loss slows. Recalculating at that point, or checking her real TDEE with a few weeks of data, keeps the plan on track.

What happens with age

The equation takes 5 kcal off for every year. For a man who is 175 cm and 80 kg, that means a BMR of 1,749 kcal at 30, 1,674 at 45, 1,599 at 60 and 1,524 at 75: a drop of 225 kcal over 45 years, if nothing else changes. In real life, other things do change. Many people lose muscle and move less, which lowers TDEE more than the age term alone. Strength training and staying active protect against most of that.

A large 2021 study using doubly labelled water found that energy use, adjusted for body size and composition, stays fairly stable from about 20 to 60 and declines after that, so the slow, steady age effect in the equation is a reasonable simplification for most adults.

How it compares with other equations

For the same person, the revised Harris-Benedict equation usually gives 60 to 120 kcal more BMR. Katch-McArdle and Cunningham, which use lean body mass, can be higher or lower depending on body fat: higher for lean people, lower for people with more fat. The formula comparison puts all four side by side.

Recalculating as your weight changes

Because weight carries a coefficient of 10, every kilo you lose takes about 10 kcal off your BMR, and 12 to 19 kcal off your TDEE depending on your activity factor. Lose 10 kg (22 lb) and your TDEE is roughly 120 to 190 kcal lower. That is why a diet that worked at the start slows down later. Recalculate after every 4 to 5 kg (10 lb), or measure your real TDEE from your log with the adaptive TDEE calculator.

Mifflin-St Jeor equation questions

Does the Mifflin-St Jeor equation give BMR or TDEE?

BMR, your resting burn. To get TDEE, multiply it by an activity factor from 1.2 (sedentary) to 1.9 (athlete).

Does Mifflin-St Jeor take body fat into account?

No. It only uses weight, height, age and sex. If you know your body fat and you are lean or muscular, a lean-mass formula such as Katch-McArdle may suit you better.

How accurate is Mifflin-St Jeor?

For most healthy adults it is within about 10% of measured resting metabolism, the best of the common equations in a major systematic review. Some individuals are further out, so check it against your weight trend.

What activity multiplier should I use with Mifflin-St Jeor?

The standard set: 1.2 sedentary, 1.375 lightly active, 1.55 moderately active, 1.725 very active and 1.9 for athletes. If you are between two, choose the lower one.

How often should I recalculate with Mifflin-St Jeor?

After every 4 to 5 kg (10 lb) of weight change, after a birthday that changes your decade if you like, and whenever your activity changes. Small changes in age barely matter.

Is Mifflin-St Jeor accurate for people with obesity?

Reasonably, yes. It was developed in a group that included people with obesity and performed well in them in later reviews. As always, confirm it with a few weeks of tracking.

Do dietitians use Mifflin-St Jeor?

Yes. After the 2005 systematic review for the American Dietetic Association found it the most reliable of the common equations, it became a standard choice for estimating the needs of healthy adults when resting metabolism can’t be measured.

Can I use Mifflin-St Jeor if I’m over 65?

Yes, though it may overestimate if you have lost a lot of muscle. Test the number for a few weeks, and consider strength training, which helps protect your metabolism.

Sources

1. Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247. doi.org/10.1093/ajcn/51.2.241
2. 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. pubmed.ncbi.nlm.nih.gov/15883556/
3. Frankenfield DC, Rowe WA, Smith JS, Cooney RN. Validation of several established equations for resting metabolic rate in obese and nonobese people. J Am Diet Assoc. 2003;103(9):1152-1159. pubmed.ncbi.nlm.nih.gov/12963943/
4. Harris JA, Benedict FG. A biometric study of human basal metabolism. Proc Natl Acad Sci USA. 1918;4(12):370-373. doi.org/10.1073/pnas.4.12.370
5. Henry CJK. Basal metabolic rate studies in humans: measurement and development of new equations. Public Health Nutr. 2005;8(7A):1133-1152. doi.org/10.1079/PHN2005801
6. Pontzer H, Yamada Y, Sagayama H, et al. Daily energy expenditure through the human life course. Science. 2021;373(6556):808-812. doi.org/10.1126/science.abe5017
7. ten Haaf T, Weijs PJM. Resting energy expenditure prediction in recreational athletes of 18-35 years: confirmation of Cunningham equation and an improved weight-based alternative. PLoS One. 2014;9(10):e108460. doi.org/10.1371/journal.pone.0108460