For most adults, Mifflin-St Jeor is the most accurate of the three common formulas. If you know your body fat percentage reliably, Katch-McArdle is a good second check. Revised Harris-Benedict tends to give slightly higher numbers.
Below are the formulas, a side-by-side test on three different people, and what the research says.
The three formulas
W = weight (kg), H = height (cm), A = age (years), BF = body fat %.
| Formula | Men | Women |
|---|---|---|
| Mifflin-St Jeor (1990) | 10W + 6.25H − 5A + 5 | 10W + 6.25H − 5A − 161 |
| Revised Harris-Benedict (1984) | 88.362 + 13.397W + 4.799H − 5.677A | 447.593 + 9.247W + 3.098H − 4.330A |
| Katch-McArdle | 370 + 21.6 × W × (1 − BF/100) | same |
Each gives BMR (basal metabolic rate). TDEE is BMR × your activity factor (1.2 to 1.9).
Side-by-side test
We calculated BMR for three example people. All numbers are rounded to the nearest kcal.
| Person | Mifflin-St Jeor | Harris-Benedict (rev.) | Katch-McArdle |
|---|---|---|---|
| Woman, 25 y, 60 kg, 160 cm, 25% body fat | 1,314 | 1,390 | 1,342 |
| Man, 30 y, 80 kg, 178 cm, 15% body fat | 1,768 | 1,844 | 1,839 |
| Man, 50 y, 105 kg, 180 cm, 32% body fat | 1,930 | 2,075 | 1,912 |
What this shows:
- Harris-Benedict is 76–145 kcal higher than Mifflin in every case.
- For the lean man, Katch-McArdle is close to Harris-Benedict, because he carries more muscle than an average man of his weight.
- For the man with higher body fat, Katch-McArdle is the lowest, because fat tissue burns far less energy at rest than muscle.
After an activity factor of 1.55, a 145 kcal BMR gap grows to about 225 kcal of TDEE. That is enough to change the speed of a diet.
What the research says
A 2005 systematic review by Frankenfield, Roth-Yousey and Compher compared predictive equations against measured resting metabolic rate. Mifflin-St Jeor was the most reliable, predicting within 10% of measured values more often than the others, in both non-obese and obese adults. Harris-Benedict tended to overestimate.
Katch-McArdle depends on lean body mass. It can be very good when body fat is measured well, for example by DEXA. If your body fat number comes from a cheap smart scale, the error in that number passes straight into the result.
Which one should you use?
| Your situation | Use |
|---|---|
| Most adults, body fat unknown | Mifflin-St Jeor |
| Lean, muscular, body fat measured by DEXA or a skilled caliper test | Katch-McArdle, compared with Mifflin |
| Comparing with an older app or clinic report | Harris-Benedict, to match their numbers |
| You want the truth for your body | Any formula as a start, then measure your real TDEE |
Why no formula is perfect
All three formulas predict an average person with your measurements. Individual metabolism varies with muscle mass, organ size, genetics and hormones. None of them can see your daily steps either. That is why we show all three on the TDEE calculator: the spread tells you how uncertain the estimate is.
Want only the Mifflin equation, with the steps shown? Tuff Search has a dedicated Mifflin-St Jeor equation calculator.
FAQ
Is the original 1919 Harris-Benedict formula still used? Rarely. The 1984 revision by Roza and Shizgal replaced it in most tools.
Why do different websites give different TDEE numbers? They use different formulas and different activity factors. Check which formula and multiplier a site uses before comparing.
Should I average the formulas? You can, but a 4-week weight log is a better tiebreaker than an average.
Sources
- Mifflin MD, et al. (1990). Am J Clin Nutr 51(2):241–247. https://pubmed.ncbi.nlm.nih.gov/2305711/
- Roza AM, Shizgal HM (1984). Am J Clin Nutr 40(1):168–182. https://pubmed.ncbi.nlm.nih.gov/6741850/
- Frankenfield D, et al. (2005). J Am Diet Assoc 105(5):775–789. https://pubmed.ncbi.nlm.nih.gov/15883556/
This article is general information for healthy adults, not medical advice.