Mifflin-St Jeor vs Harris-Benedict: Which Is More Accurate
If you've used more than one TDEE calculator, you've probably noticed they give different numbers. The reason: they use different BMR formulas under the hood. The two most common are Mifflin-St Jeor (1990) and Harris-Benedict (revised by Roza & Shizgal, 1984). The difference typically ranges from 50-200 calories — small enough to seem insignificant, but large enough to make or break a tight deficit over weeks.
The newer, ADA-recommended formula. Uses weight, height, age, and sex. Validated against indirect calorimetry in multiple studies.
Pros
- Predicted BMR within 10% for 82% of subjects in the ADA's 2005 comparative review
- Better accuracy across both normal-weight and obese populations
- Recommended by the American Dietetic Association as the standard for clinical use
- Simpler formula with fewer coefficients
Cons
- Doesn't account for body composition (lean mass vs fat mass)
- May underestimate for very muscular individuals
- Less accurate for underweight individuals (BMI < 18.5)
General population, anyone without a body fat percentage measurement, clinical and research settings
The older standard, revised in 1984 from the original 1919 formula. Uses the same inputs. Tends to estimate ~5% higher than Mifflin-St Jeor.
Pros
- Long track record — the original (1919) is one of the most cited equations in nutrition science
- 1984 revision improved accuracy over the original
- May be more accurate for underweight individuals
Cons
- Overestimates BMR by ~5% on average compared to measured values
- Only predicted BMR within 10% for 69% of subjects in the ADA review
- Higher error rate in obese individuals — overestimates more as body fat increases
- No longer the ADA's recommended formula
Historical comparison, checking if your Mifflin-St Jeor result seems low, underweight individuals
Decision Table
See the tradeoffs side by side
| Criterion | Mifflin-St Jeor (1990) | Harris-Benedict Revised (1984) |
|---|---|---|
| ADA recommendation | Recommended as primary formula | No longer preferred |
| Accuracy (within 10% of measured) | 82% of subjects | 69% of subjects |
| Typical bias | Slight underestimate (~2%) | Overestimates by ~5% |
| Year published | 1990 | 1984 (revised from 1919) |
| Uses body fat %? | No | No |
| Best alternative if body fat known | Katch-McArdle (uses lean mass) | Katch-McArdle (uses lean mass) |
Verdict
Use Mifflin-St Jeor as your primary formula — it's what the ADA recommends and what our TDEE Calculator uses as its default. But run both and check the Formula Comparison tab to see the range. If they agree within 100 calories, you have a solid estimate. If they disagree by 200+, your profile is harder to estimate and you should calibrate with 2-3 weeks of real-world tracking. And if you know your body fat percentage, add it to enable Katch-McArdle — it bypasses the height/weight limitations of both formulas entirely.
FAQ
Questions people ask next
The short answers readers usually want after the first pass.
Mifflin-St Jeor vs Harris-Benedict: which is more accurate?
Can I just average the two formulas?
What about the Katch-McArdle formula?
Why do some apps use Harris-Benedict by default?
Sources & References
- Comparison of Predictive Equations for Resting Metabolic Rate in Healthy Nonobese and Obese Adults — Journal of the American Dietetic Association (2005) — Frankenfield et al.
- A new predictive equation for resting energy expenditure in healthy individuals — American Journal of Clinical Nutrition (1990) — Mifflin et al.
- The Harris Benedict equation reevaluated — American Journal of Clinical Nutrition (1984) — Roza & Shizgal
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