The Mifflin–St Jeor equation estimates BMR as 10 × weight (kg) + 6.25 × height (cm) − 5 × age, plus 5 for men or minus 161 for women. It is the most reliable height-and-weight formula for most adults. Harris–Benedict runs about 4–7% higher, while Katch–McArdle (370 + 21.6 × lean mass in kg) is better when you know your body fat.
Key takeaways
- Mifflin–St Jeor is the best default; in a systematic review it was the most often accurate of the common equations.
- Both Harris–Benedict versions give higher results than Mifflin for the four example people, by roughly 4–7%.
- Katch–McArdle and Cunningham use lean mass, so they need a body-fat estimate and ignore age and sex.
- Cunningham is designed for very active people and gives the highest value for every example person.
- The gap between equations is much smaller than the error in the activity factor you multiply by.
BMR formulas all answer one question: how many calories does your body burn at rest? Enter your numbers once in the calculator below, or read on for each equation, the exact coefficients and a side-by-side comparison. For the full TDEE, use the TDEE calculator.
What is the Mifflin–St Jeor equation?
The Mifflin–St Jeor equation was published in 1990 and is the default in most modern calculators because it predicted measured resting energy best in a systematic review (Mifflin et al., 1990; Frankenfield et al., 2005).
Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
The −161 constant is the female version of the equation. For results built around women, see the TDEE calculator for women, or the BMR calculator for women over 50 for later life.
What are the Harris–Benedict equations?
The original Harris–Benedict equations date from 1918 (Harris & Benedict, 1918). Roza and Shizgal refitted the coefficients in 1984 (Roza & Shizgal, 1984). Both versions are below, exactly as TDEECalc implements them.
Original (1918) Men: BMR = 66.473 + 13.7516 × weight(kg) + 5.0033 × height(cm) − 6.755 × age Women: BMR = 655.0955 + 9.5634 × weight(kg) + 1.8496 × height(cm) − 4.6756 × age
Revised (Roza–Shizgal, 1984) Men: BMR = 88.362 + 13.397 × weight(kg) + 4.799 × height(cm) − 5.677 × age Women: BMR = 447.593 + 9.247 × weight(kg) + 3.098 × height(cm) − 4.33 × age
What are the Katch–McArdle and Cunningham equations?
These use lean body mass instead of height, age and sex (McArdle, Katch & Katch; Cunningham, 1980). Lean mass is body weight times one minus your body-fat fraction.
lean mass(kg) = weight(kg) × (1 − body fat % ÷ 100) Katch–McArdle: BMR = 370 + 21.6 × lean mass(kg) Cunningham: BMR = 500 + 22 × lean mass(kg)
How do the five formulas compare?
Here are the BMRs (kcal/day) for four example people, each calculated with all five equations.
| Person | Mifflin–St Jeor | Harris–Benedict revised | Harris–Benedict original | Katch–McArdle | Cunningham |
|---|---|---|---|---|---|
| Woman, 28, 5′4″ (162.6 cm), 140 lb (63.5 kg), 25% body fat | 1,350 | 1,417 | 1,432 | 1,399 | 1,548 |
| Woman, 35, 5′5″ (165.1 cm), 165 lb (74.8 kg), 30% body fat | 1,444 | 1,500 | 1,513 | 1,502 | 1,653 |
| Man, 30, 5′10″ (177.8 cm), 190 lb (86.2 kg), 20% body fat | 1,828 | 1,926 | 1,939 | 1,859 | 2,017 |
| Man, 45, 6′0″ (182.9 cm), 230 lb (104.3 kg), 28% body fat | 1,966 | 2,108 | 2,112 | 1,992 | 2,153 |
What stands out:
- Mifflin–St Jeor is the lowest of the height-and-weight equations. Revised Harris–Benedict is about 4–7% higher, and the original is about 5–7% higher.
- Katch–McArdle lands close to Mifflin for these four people, within 1–4%, once a body-fat figure is plugged in.
- Cunningham is consistently highest, about 10–15% above Mifflin here. It was built from data on active people, so it can overstate resting energy for sedentary people.
Multiply any of these by an activity factor to reach TDEE. For the 35-year-old woman, Mifflin gives 2,239 kcal at ×1.55 while Cunningham would give 2,562. That 323 kcal gap is why the formula you pick matters, but not as much as the activity factor you pick.
Worked example: Mifflin–St Jeor by hand
For the man in the table (30 years old, 177.8 cm, 86.18 kg):
| Step | Calculation | Result |
|---|---|---|
| Weight term | 10 × 86.18 | 862 |
| Height term | 6.25 × 177.8 | 1,111 |
| Age term | −5 × 30 | −150 |
| Sex constant | men | +5 |
| BMR | 862 + 1,111 − 150 + 5 | 1,828 kcal |
Now Katch–McArdle for the same man at 20% body fat. Lean mass is 86.18 × 0.80 = 68.9 kg, so BMR = 370 + 21.6 × 68.9 = 1,859 kcal, within 2% of Mifflin. Lean-mass equations matter most when body composition is unusual, for example a very muscular or very lean person, which is the case they exist for. If you do not know your lean mass, the lean body mass calculator estimates it.
Which BMR formula should you use?
| Your situation | Use |
|---|---|
| Most adults, no body-fat figure | Mifflin–St Jeor |
| Reliable body-fat estimate, lean or muscular | Katch–McArdle |
| Highly trained athlete with measured body fat | Cunningham, then check against your weight trend |
| Comparing with an older chart or textbook | Harris–Benedict (revised) |
| Any case | Check the result against your actual weight trend after 3–4 weeks |
A formula cannot see your individual metabolism, so the end test is always your results; see how accurate TDEE calculators are. For BMR basics, read TDEE vs BMR.
Frequently asked questions
What is the Mifflin–St Jeor equation?
It is a 1990 equation for resting energy expenditure: 10 × weight in kg + 6.25 × height in cm − 5 × age + 5 for men, or − 161 for women. It was derived from measurements on healthy adults, and a later systematic review found it the most reliable of the common equations for non-obese and obese adults.
Mifflin–St Jeor vs Harris–Benedict: which is better?
Mifflin–St Jeor, for most modern adults. Harris–Benedict dates from 1918 (revised in 1984) and tends to give higher numbers, about 4–7% for the four people compared here. If you want to see both for your own stats, use the BMR calculator.
What is the difference between original and revised Harris–Benedict?
Same idea, different coefficients. The 1984 Roza–Shizgal revision refitted the original 1918 equation with updated coefficients. In our four examples the revised version comes out a little lower than the original, by about 4–15 kcal.
When should I use Katch–McArdle?
Use Katch–McArdle or Cunningham when you have a reasonable body-fat estimate, particularly if you are very muscular or quite lean, where height-and-weight equations misjudge lean mass. If your body-fat figure is a guess, the output is only as good as the guess. Try the body fat calculator.
Do I multiply BMR by an activity factor with every formula?
Yes. All five equations estimate resting energy only. To get TDEE, multiply by 1.2 to 1.9 depending on activity. Apply the same factors to any of them, then check the result against your weight trend; Cunningham in particular can run high for people who are not very active.
Why do different calculators give different BMRs?
They use different equations, and some round or convert units differently. A gap of 50–200 kcal between formulas is normal. Pick one, stay with it, and adjust based on your results using adaptive TDEE.
References
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO (1990). A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition 51(2):241–247.
- Frankenfield D, Roth-Yousey L, Compher C (2005). Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association 105(5):775–789.
- Harris JA, Benedict FG (1918). A biometric study of human basal metabolism. Proceedings of the National Academy of Sciences 4(12):370–373.
- Roza AM, Shizgal HM (1984). The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. American Journal of Clinical Nutrition 40(1):168–182.
- McArdle WD, Katch FI, Katch VL (2015). Exercise Physiology: Nutrition, Energy, and Human Performance (8th ed.). Wolters Kluwer Health.
- Cunningham JJ (1980). A reanalysis of the factors influencing basal metabolic rate in normal adults. American Journal of Clinical Nutrition 33(11):2372–2374.