Search "calorie calculator formula" and most results still use Harris-Benedict, a formula derived from a study published in 1919. It's not that it's wildly wrong — it's that a more accurate, modern formula has existed since 1990 and most calculators simply never switched.
A 30-year-old male, 80kg, 180cm:
| Formula | Year | BMR |
|---|---|---|
| Harris-Benedict | 1919 (revised 1984) | 1,854 kcal |
| Mifflin-St Jeor | 1990 | 1,780 kcal |
A 74 kcal/day gap doesn't sound large, but it compounds: built into a "maintenance calories" figure and then used as the base for a weight-loss target, a consistent 74 kcal/day overestimate is enough to stall or reverse someone's progress over months, especially at smaller deficits.
Harris-Benedict was built from a small, non-representative sample over a century ago. Mifflin-St Jeor was derived from a larger, more modern dataset and has been repeatedly validated as more accurate for the general population since — it's the formula registered dietitians default to in practice, not just a marginally different alternative.
Mifflin-St Jeor BMR, full TDEE with activity level, and a target calorie range — not the century-old formula.
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