Mifflin vs Harris-Benedict: Which BMR Formula Belongs in Your Diet

Estimated reading: 5 min

Open your calculator, enter yourself into two popular BMR equations, and you will get two different starting points. One says plan around 1,682 kcal, the other says 1,703. That 20-kcal gap looks trivial, but it hints at a more important reality: the equations were built decades apart, on different people, and one of them is systematically more accurate for modern bodies. Here is the head-to-head you need before you set a single calorie target.

The Two Formulas Side by Side

Mifflin-St Jeor, published in 1990, works out to 10 times weight in kilograms, plus 6.25 times height in centimeters, minus 5 times age, plus 5 for men (or minus 161 for women). Harris-Benedict in its revised 1984 form uses a heavier constant and larger weight term: 13.397 times weight for men, plus 4.799 times height, minus 5.677 times age, added to 88.362. Run both on a 30-year-old male, 175 cm, 70 kg, and you get about 1,682 kcal from Mifflin and roughly 1,703 kcal from Harris-Benedict.

Why One Tends to Run Higher

The 1984 Harris-Benedict revision grew out of an older body of research and, across many comparison studies, tends to overshoot resting energy expenditure for typical adults. Mifflin-St Jeor was derived from a more modern sample and consistently lands closer to measured values in controlled studies, which is why the Academy of Nutrition and Dietetics recommends it as the most accurate equation for resting metabolic rate in healthy, non-obese adults. When two estimates disagree, the more accurate one is the better budgeting tool.

What the Gap Means for Weight Loss

Imagine you build a diet off a base that is inflated by 20 to 40 kcal or more. Over a full dieting phase, an overestimated BMR nudges your maintenance number up, and a deficit calculated on top of it shrinks silently. You might cut to what feels like a surplus-adjusted target and lose weight more slowly than planned, then chase your tail for weeks. Mifflin's accuracy advantage removes that hidden drift, which matters more the longer you cut.

A Worked Comparison for Your Scroll

Take Maya, a 28-year-old woman, 165 cm, 60 kg. Mifflin-St Jeor gives her BMR ≈ 1,364 kcal. The revised Harris-Benedict equation yields about 1,396 kcal. At a moderate activity factor of 1.55, maintenance differs by roughly 50 kcal — 2,114 vs 2,164. For fat loss, cutting 500 kcal leaves Maya near 1,614 on the Mifflin plan versus about 1,664 on Harris-Benedict. Neither breaks her diet, but Mifflin's baseline demands fewer calories to lose at the same pace, matching what measurement studies say she actually burns.

The Bottom Line for Dieters

For general weight-loss planning, default to Mifflin-St Jeor: it is the modern, Academy-endorsed benchmark and the default on the BMRScope calculator. Treat Harris-Benedict as a useful cross-check when you want to see whether your result is stable. Whichever you choose, treat it as a starting estimate, track honestly for two to three weeks, and adjust. The right formula simply gives you a cleaner starting line — and that is a genuine edge on the way to your goal.