If you have ever looked up how many calories you burn at rest, the number most likely came from the Mifflin-St Jeor equation. Published in 1990 in the American Journal of Clinical Nutrition, it replaced the 70-year-old Harris-Benedict equation as the standard in many clinics because it was built on a more modern population and proved more reliable when tested. It needs four inputs (weight, height, age and sex) and returns your resting energy expenditure, the calories your body uses lying still. This calculator applies it, converts the result to kilojoules and per hour, and scales it by four activity levels to give daily calorie needs.
How to use the Mifflin-St Jeor calculator
- Select sex and enter your age.
- Enter your height and weight in whatever units you have.
- Read resting energy in kcal and kJ per day and kcal per hour.
- Pick the daily figure that matches your usual activity from the four rows.
Mifflin-St Jeor formula
Women: REE = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161
Daily calories = REE × activity multiplier
| Activity level (IOM 2005) | PAL range | Multiplier used here |
|---|---|---|
| Sedentary | 1.0 – 1.39 | 1.2 |
| Low active | 1.4 – 1.59 | 1.5 |
| Active | 1.6 – 1.89 | 1.75 |
| Very active | 1.9 – 2.5 | 2.2 |
Source: Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition 1990;51:241–247. The authors studied 498 healthy adults, 251 men and 247 women. The activity categories are from the Institute of Medicine’s Dietary Reference Intakes for Energy (2005).
Worked example
A 35-year-old man, 180 cm and 80 kg.
- REE = 10 × 80 + 6.25 × 180 − 5 × 35 + 5 = 800 + 1,125 − 175 + 5 = 1,755 kcal/day
- In kilojoules: 1,755 × 4.184 = 7,343 kJ/day; per hour 73.1 kcal
- Daily calories: sedentary 2,106, low active 2,632, active 3,071, very active 3,861 kcal.
Resting energy by age and sex
For a 70 kg adult (165 cm woman, 178 cm man). The age term subtracts 5 kcal for each year.
| Sex (70 kg) | Age | Resting energy (kcal/day) | Resting energy (kJ/day) |
|---|---|---|---|
| Woman | 20 | 1,470 | 6,152 |
| Woman | 30 | 1,420 | 5,942 |
| Woman | 40 | 1,370 | 5,733 |
| Woman | 50 | 1,320 | 5,524 |
| Woman | 60 | 1,270 | 5,315 |
| Woman | 70 | 1,220 | 5,106 |
| Man | 20 | 1,718 | 7,186 |
| Man | 30 | 1,668 | 6,977 |
| Man | 40 | 1,618 | 6,768 |
| Man | 50 | 1,568 | 6,558 |
| Man | 60 | 1,518 | 6,349 |
| Man | 70 | 1,468 | 6,140 |
How accurate is Mifflin-St Jeor?
In the systematic review by Frankenfield and colleagues (J Am Diet Assoc 2005;105:775–789), Mifflin-St Jeor predicted measured resting metabolic rate within 10 percent for a larger share of both non-obese and obese adults than the Harris-Benedict, Owen and WHO equations, and it had the narrowest spread of errors. Even so, the review reported that around a quarter to a third of individuals were off by more than 10 percent, and the equation can under- or over-predict in athletes, in older adults and in people with unusual body composition.
Strengths and limits
- Strengths. Simple, validated in several large samples, applicable across a wide range of weights.
- Limits. It ignores body composition; two people with the same measurements but different lean mass have different true rates.
- Not for children. It was developed in adults.
- The activity step is the weakest link. Multipliers are broad averages.
Next steps
For comparison with other equations see the RMR Calculator, Harris-Benedict Calculator and BMR Calculator. To plan intake use the Calorie Calculator, TDEE Calculator and Maintenance Calorie Calculator.
This page is for information only and is not medical or dietary advice. Speak to a doctor or registered dietitian about your own needs.
Sources
- Mifflin MD, et al. Am J Clin Nutr 1990;51:241–247.
- Frankenfield D, et al. J Am Diet Assoc 2005;105:775–789.
- Institute of Medicine. Dietary Reference Intakes for Energy, 2005.
Frequently asked questions
What is the Mifflin-St Jeor equation?
It is a formula published in 1990 by Mifflin, St Jeor and colleagues that predicts resting energy expenditure from weight, height, age and sex. It has since become the most widely used equation by dietitians in the United States.
How was it developed?
The authors measured resting energy expenditure in 498 healthy people (251 men and 247 women, aged 19 to 78) with a range of body weights, including obese individuals, using indirect calorimetry, then fitted a regression equation. The updated population is one reason it works better than the older Harris-Benedict equation in modern groups.
How accurate is it?
A 2005 systematic review for the American Dietetic Association (Frankenfield et al.) found it predicted resting metabolic rate within 10 percent of the measured value in more non-obese and obese adults than other equations tested. For an individual the error can still be larger.
Why does it use kilograms and centimetres?
The coefficients were fitted to metric data. The calculator converts pounds and inches for you so you can enter the units you know.
Does the equation apply to athletes and older adults?
It was developed in people up to 78, but it does not account for muscle or fat mass, so very muscular or very lean people may be mis-estimated; the Katch-McArdle equation in the BMR Calculator uses lean mass instead.