THE NUMORIX GUIDE
How to use the Metabolic Age Calculator
Last reviewed September 14, 2026
What this calculator does
The engine normalizes BMR as x = BMR / 1000 and calculates metabolic age = round(14.
Formula and method
The engine normalizes BMR as x = BMR / 1000 and calculates metabolic age = round(14.7 * x^2 - 15.3 * x + 42.2). It then subtracts actual age to produce the difference and uses fixed bands: below -3 younger, -3 through 2 close, 3 through 7 slower, and 8 or more significantly higher.
Variables and inputs
Enter BMR in kcal/day and actual age in years. The route does not request sex, height, weight, body composition, activity, or the equation used to obtain BMR, even though all of those can affect a BMR estimate.
Worked example
For the defaults of BMR 1,650 kcal/day and actual age 35: x = 1.65; 14.7 * 1.65^2 - 15.3 * 1.65 + 42.2 = 56.98, which rounds to metabolic age 57. Difference = 57 - 35 = +22 years, so the engine returns its significantly higher interpretation.
How to interpret the result
Metabolic age is a consumer-facing comparison produced by this polynomial, not a recognized measurement of biological age or metabolic health. A higher or lower number does not independently diagnose a slow metabolism, fitness level, or disease.
Common mistakes to avoid
Use BMR in kcal/day rather than TDEE or a body weight, and keep actual age in years. Do not compare results generated from different BMR equations as though the inputs were measured on the same scale.
Assumptions and limitations
The polynomial is hardcoded and has no displayed validation, sex term, height term, weight term, body-composition term, activity term, reference population, or clinical calibration. Its interpretation labels are arbitrary thresholds, and any error in the BMR input carries into the age result. It should not guide treatment or aggressive dieting.