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Mifflin-St Jeor vs Harris-Benedict BMR Calculator
Which BMR formula should you trust — Mifflin-St Jeor or Harris-Benedict? This calculator runs both so you can compare, and the short answer is Mifflin. The Mifflin-St Jeor equation (1990) is the most accurate for most people, while the revised Harris-Benedict equation is older and tends to overestimate BMR by roughly 5–15%, especially in sedentary people. For a 30-year-old man of 80 kg and 180 cm, Mifflin gives a BMR of about 1,780 kcal; Harris-Benedict gives about 1,854 — that 4% gap compounds once you multiply by an activity factor for TDEE. Switch the formula toggle to see both, then multiply by your activity level (1.2–1.9) for TDEE and apply your goal for cut, maintain or bulk calories. Every value is shown in kcal. Unless you have a specific reason to prefer Harris-Benedict, use Mifflin. This is a fitness estimate, not medical or dietary advice.
Mifflin-St Jeor (1990) — most accurate for most people (the default)
- Harris-Benedict (revised) — overestimates BMR by ~5–15%
- Example: male 80 kg / 180 cm / 30 y → Mifflin 1,780 vs Harris-Benedict ≈ 1,854 kcal
Frequently asked questions
Is Mifflin-St Jeor or Harris-Benedict more accurate?
Mifflin-St Jeor (1990) is more accurate for most people and is the recommended default. The revised Harris-Benedict equation is older and tends to overestimate BMR by about 5–15%, particularly in sedentary individuals. For the same person the two can differ by a few percent, and that gap grows once you multiply by an activity factor to get TDEE.
When would I use Harris-Benedict instead?
Rarely by preference — it is mainly useful for comparison or continuity with older tools and studies. If you want the most accurate estimate and know your body-fat percentage, Katch-McArdle (based on lean mass) can beat both; otherwise use Mifflin-St Jeor.