Metabolic Formula Comparison
Mifflin-St Jeor
vs Katch-McArdle
Which formula should you use to estimate Basal Metabolic Rate (BMR)? We break down the mathematical differences, inputs required, and accuracy profiles of the two industry-standard metabolic equations.
By BodyCompOS Editorial Board·Metabolic equations peer review
Published June 2026•Last Updated: June 27, 2026•Refs: Mifflin et al. 1990, Katch & McArdle 1996
| Feature | Mifflin-St Jeor | Katch-McArdle |
|---|---|---|
| Primary Driver | Total body weight, height, age, sex | Lean Body Mass (LBM) only |
| Accuracy (General) | Very high for standard populations | Extremely high for lean/athletic build |
| Requires Body Fat % | No | Yes (mandatory) |
| Accounts for Aging | Yes (subtracts calories as age increases) | Indirectly (through muscle mass changes) |
Which Formula is Best for You?
Use Mifflin-St Jeor if you do not know your current body fat percentage. It uses easily measured demographic variables (height, weight, age, sex) to estimate resting metabolic rate with high reliability.
Choose Katch-McArdle if you have a reliable estimate of your body fat percentage (e.g. from skinfold calipers or DXA scans). Because it calculates metabolic rate based solely on lean tissue mass, it avoids over-estimating energy requirements for high-body-fat individuals and under-estimating requirements for highly muscular athletes.
TDEE calculator
Our TDEE Calculator automatically selects Katch-McArdle when body fat inputs are supplied, falling back to Mifflin-St Jeor otherwise.
TDEE Calculator