BMR equations compared: Mifflin-St Jeor vs Harris-Benedict vs Katch-McArdle

For a 40-year-old man of 80 kg and 170 cm, the revised Harris-Benedict equation gives 1,749 kcal/day and Mifflin-St Jeor 1,668, 81 lower (4.7 percent). Katch-McArdle at 25 percent body fat gives 1,666. At 130 kg the first two give him 2,419 and 2,168, and a woman of his age and height 2,003 and 2,002.

Line chart of BMR against body weight from 50 to 130 kg for a man of 40, 170 cm tall. Revised Harris-Benedict rises from 1,347 to 2,419 kcal/day and Mifflin-St Jeor from 1,368 to 2,168; the two lines cross at 56.0 kg and are 251 apart at 130 kg. Katch-McArdle at 25 percent body fat rises from 1,180 to 2,476, crossing Mifflin-St Jeor at 80.2 kg, and at 35 percent from 1,072 to 2,195, crossing it at 123.1 kg. — BMR against body weight for a man of 40, 170 cm tall, by each equation. Each Katch-McArdle line holds body fat fixed from 50 to 130 kg, though few adults of 170 cm weigh 50 kg at 35 percent fat or 130 kg at 25 percent; read Katch-McArdle at a measured body fat, as in the body fat table. Every plotted point is a row of the table. Image © ScienceQuest, CC BY 4.0: free to reuse with credit and a link to this page, as the image licence explains.

BMR by body weight

BMR in kcal/day by body weight at 40 years and 170 cm, by Mifflin-St Jeor and revised Harris-Benedict for each sex, and Katch-McArdle at 25 and 35 percent body fat
Weight (kg)	Women		Men		Katch-McArdle, either sex
Weight (kg)	Mifflin	Harris-Benedict	Mifflin	Harris-Benedict	25% fat	35% fat
50	1,202	1,263	1,368	1,347	1,180	1,072
60	1,302	1,356	1,468	1,481	1,342	1,212
70	1,402	1,448	1,568	1,615	1,504	1,353
80	1,502	1,541	1,668	1,749	1,666	1,493
90	1,602	1,633	1,768	1,883	1,828	1,634
100	1,702	1,726	1,868	2,017	1,990	1,774
110	1,802	1,818	1,968	2,151	2,152	1,914
120	1,902	1,911	2,068	2,285	2,314	2,055
130	2,002	2,003	2,168	2,419	2,476	2,195

Whole kcal/day for reading across a row; multiply by 4.184 for kJ/day: 2,000 kcal/day is 8,368 kJ/day. The Katch-McArdle columns keep one body fat at every weight, which few people do.

BMR by age

BMR in kcal/day by age at 70 kg and 170 cm, by Mifflin-St Jeor and revised Harris-Benedict for each sex, with Harris-Benedict minus Mifflin-St Jeor
Age (years)	Women			Men
Age (years)	Mifflin	Harris-Benedict	Gap	Mifflin	Harris-Benedict	Gap
20	1,502	1,535	+33	1,668	1,728	+61
30	1,452	1,492	+40	1,618	1,672	+54
40	1,402	1,448	+47	1,568	1,615	+47
50	1,352	1,405	+54	1,518	1,558	+41
60	1,302	1,362	+60	1,468	1,501	+34
70	1,252	1,318	+67	1,418	1,445	+27
80	1,202	1,275	+74	1,368	1,388	+20

We work each gap from the unrounded estimates, so it can differ by 1 from the rounded cells. Mifflin’s sample stopped at 78, so the 80 row lies outside it [1].

BMR by body fat

Katch-McArdle against Mifflin-St Jeor for a man of 80 kg, 178 cm and 35 years as his body fat changes, in kcal/day
Body fat (%)	Lean mass kg	Katch-McArdle kcal/day	Mifflin-St Jeor kcal/day	Katch minus Mifflin kcal/day
10	72.0	1,925	1,743	+183
15	68.0	1,839	1,743	+96
20	64.0	1,752	1,743	+10
25	60.0	1,666	1,743	−77
30	56.0	1,580	1,743	−163
35	52.0	1,493	1,743	−249

For him Mifflin-St Jeor gives 1,743 and Harris-Benedict 1,816 at any body fat.

All three are population estimates of resting energy expenditure, fitted to groups of measured adults. Your own rate can sit outside every column here; only indirect calorimetry measures it. A 2005 review of Harris-Benedict, Mifflin-St Jeor and two other equations found older adults and US ethnic minorities underrepresented in their development and validation [5].

Why the formulas disagree

Harris and Benedict’s 1918 paper analysed 136 men and 103 women measured over a decade at the Carnegie Nutrition Laboratory [3]. In 1984 Roza and Shizgal refitted the equations with 98 more subjects from a series Benedict published later, which spanned a wider age range [2]. Mifflin’s team measured 498 adults aged 19 to 78, 234 of them obese, and found the original Harris-Benedict equations 5 percent above the REE they measured [1]; the tables here use the 1984 revision. Mifflin and Cunningham fitted resting energy expenditure, which calculators label BMR, while Harris and Benedict measured basal metabolism 12 to 14 hours after the last meal, in complete muscular repose [3].

Each kilogram adds 10 kcal/day in Mifflin-St Jeor, 13.4 in Harris-Benedict for a man and 9.2 for a woman. So at 40 and 170 cm a man’s gap grows 3.4 kcal/day per kg, from −21 at 50 kg to +251 at 130 kg, and a woman’s shrinks 0.75 per kg. Each year of age takes 5.7 kcal/day off a man in Harris-Benedict, 4.3 off a woman and 5 off either in Mifflin-St Jeor, so at 70 kg the men’s gap falls from 61 at 20 to 20 at 80, while the women’s grows from 33 to 74.

Katch-McArdle has no term for sex, age or height; its one input is lean mass, at 21.6 kcal/day per kilogram [4]. Calculators label 370 + 21.6 × lean mass Katch-McArdle, and we cite it to Cunningham’s 1991 review, where the equation appears. For the man in the body fat table it matches Mifflin-St Jeor at 20.6 percent fat, and every 5 points of body fat move it by 86 kcal/day. So a body fat figure 5 points off moves his estimate by more than the 73 kcal/day that separates Harris-Benedict from Mifflin-St Jeor for him.

The formulas

Mifflin-St Jeor [1]: $\mathrm{REE} = 10\,m + 6.25\,h - 5\,a + 5\ \text{(men)},$ $\mathrm{REE} = 10\,m + 6.25\,h - 5\,a - 161\ \text{(women)}$
Harris-Benedict, revised by Roza and Shizgal [2]: $\mathrm{REE} = 88.362 + 13.397\,m + 4.799\,h - 5.677\,a\ \text{(men)},$ $\mathrm{REE} = 447.593 + 9.247\,m + 3.098\,h - 4.330\,a\ \text{(women)}$
Katch-McArdle (Cunningham’s equation) [4]: $\mathrm{REE} = 370 + 21.6\,\mathrm{LBM},$ $\mathrm{LBM} = m\left(1 - \frac{f}{100}\right)$

REE is resting energy expenditure in kcal/day, m is weight in kg, h height in cm, a age in years and f body fat in percent; LBM is lean body mass in kg.

Where each formula holds

Each formula’s sample, the people it holds for, and where it does not apply
Formula	Fitted in	Holds for	Not for
Mifflin-St Jeor	498 healthy adults aged 19 to 78, 264 of normal weight and 234 obese, REE by indirect calorimetry [1]	Healthy adults of normal weight and with obesity [1]; within 10 percent of measured in more of them than Harris-Benedict or Owen in a 2005 review, which did not test Katch-McArdle [5]	Children, ages outside 19 to 78, and people who are ill, since Mifflin’s sample was healthy [1]
Harris-Benedict, revised	Harris and Benedict’s 136 men and 103 women [3], with 98 more from a series Benedict published later [2]	Normally nourished adults, to a stated precision of ±14 percent [2]	Malnourished patients, for whom Roza and Shizgal found it unreliable [2]. Harris and Benedict tabulated the original equations for ages 21 to 70, heights 151 to 200 cm and weights 25.0 to 124.9 kg [3]; the 98 added subjects spanned a wider age range [2]
Katch-McArdle (Cunningham)	A review of published studies relating REE to fat-free mass in adults [4]	Adults over a broad range of weights, when fat-free mass is known; it explained 65 to 90 percent of the variation in REE [4]	Anyone without a measured body fat figure, since its error follows the error in that figure; obese women, in whom fat mass may add to the prediction [4]

Calculators and simulators

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. doi:10.1093/ajcn/51.2.241
Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr 1984;40(1):168-182. doi:10.1093/ajcn/40.1.168
Harris JA, Benedict FG. A biometric study of human basal metabolism. Proc Natl Acad Sci USA 1918;4(12):370-373. The original equations and sample. doi:10.1073/pnas.4.12.370
Cunningham JJ. Body composition as a determinant of energy expenditure: a synthetic review and a proposed general prediction equation. Am J Clin Nutr 1991;54(6):963-969. doi:10.1093/ajcn/54.6.963
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. doi:10.1016/j.jada.2005.02.005