Free Tool
BMR Calculator
Enter your weight, height, age, and sex. We calculate your BMR with every major equation in clinical use, so you can see the disagreement between them at a glance. Add body fat percent for the most accurate equations.
New to BMR? Read the plain-English definition →
Your body
Estimated BMR
All 4 equations compared. The recommended equation for your inputs is highlighted.
| Method | BMR |
|---|---|
Mifflin-St JeorBest fit Mifflin & St Jeor (1990), Am J Clin Nutr 51(2):241-7 | 1783 kcal/day |
Harris-Benedict (revised) Roza & Shizgal (1984), Am J Clin Nutr 40(1):168-82 | 1865 kcal/day |
Katch-McArdle Katch & McArdle (1996), Exercise Physiology | Needs body fat % |
Cunningham Cunningham (1991), Am J Clin Nutr 54(6):963-9 | Needs body fat % |
Auto-update your BMR as your weight changes
Zealova recalculates your BMR every time you log weight, then adjusts your daily calorie and macro targets the same day.
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Methodology + Sources
- Mifflin MD, St Jeor ST et al. (1990). A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 51(2):241-7.
- Roza AM, Shizgal HM (1984). The Harris Benedict equation reevaluated. Am J Clin Nutr 40(1):168-82.
- Katch FI, McArdle WD (1996). Exercise Physiology: Energy, Nutrition, and Human Performance.
- Cunningham JJ (1991). Body composition as a determinant of energy expenditure. Am J Clin Nutr 54(6):963-9.
- Frankenfield D et al. (2005). Comparison of predictive equations for resting metabolic rate in healthy adults. J Am Diet Assoc 105(5):775-89.
Last updated: 2026-05-14
Built by Sai, founder of Zealova. Not a neutral third party. Calculator results are estimates. For medical decisions, consult a qualified professional.
Frequently asked questions
Which BMR equation is most accurate?+
For the general population, Mifflin-St Jeor (1990) is the current gold standard. It outperformed Harris-Benedict in a 2005 American Dietetic Association meta-analysis. For lean and athletic users with a known body fat percent, Katch-McArdle is more accurate because it scales with lean mass.
Should I use Katch-McArdle or Mifflin?+
If you know your body fat percent within a few points, use Katch-McArdle. It accounts for the fact that muscle burns more calories at rest than fat does. If you do not have a recent body fat measurement, stick with Mifflin-St Jeor.
Why do the equations disagree by 100 to 300 kcal?+
Each equation was fit on a different study population in a different era. Harris-Benedict (1919, revised 1984) used a smaller, older sample. Mifflin used a larger, more representative sample in 1990. Katch-McArdle assumes you have an accurate body fat measurement. The spread across equations is roughly your real measurement uncertainty.
Do I add my workouts on top of BMR?+
No. BMR is the resting baseline only. To get your full daily calorie burn, multiply BMR by an activity factor. Use our TDEE calculator for that.
How accurate is any equation versus a metabolic cart?+
Indirect calorimetry (the lab gold standard) has an error of around 2 percent. Predictive equations have an error of 5 to 15 percent at the individual level. They are good enough to set a starting point and adjust from weekly weight trend.
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