Metabolic Age Estimate Calculator
Estimate your metabolic age by comparing your basal metabolic rate to a lean reference peer — a body-composition twist on your calendar age.
How it works
LBM = weight·(1 − bodyfat%) · BMR = 370 + 21.6·LBM (Katch-McArdle) · reference BMR uses a lean-peer body fat (18% M / 25% F) · metabolic age = age + (BMR_ref − BMR_you) ÷ 5
Metabolic age compares how much energy your body burns at rest with what a fitter reference person of the same weight would burn. Because muscle burns more than fat, a leaner body has a higher resting metabolism and reads as “younger”, while a higher-fat body reads as older. We estimate your basal rate from lean mass and translate the gap versus a lean peer into years. It is a motivational estimate, not a clinical age.
Worked example
A 30-year-old man weighing 80 kg at 20% body fat has 64 kg of lean mass and a BMR of 370 + 21.6·64 ≈ 1,752 kcal. A lean peer at 18% fat would burn ≈ 1,787 kcal, so the 35 kcal gap adds about 7 years — a metabolic age near 37.
Frequently asked questions
Is metabolic age a real medical measure?
No. It is a wellness concept popularised by body-composition scales, not a diagnostic figure. It is useful mainly as a simple, motivating way to see how body composition affects your resting metabolism.
How can I lower my metabolic age?
Building or preserving muscle raises lean mass and resting metabolism, while reducing excess body fat narrows the gap to the lean reference. Strength training plus adequate protein is the most direct lever.
Why do I need a body-fat percentage?
Two people of the same weight can have very different amounts of muscle and fat. Body fat lets the tool estimate lean mass — the tissue that actually drives resting energy expenditure — rather than assuming everyone of the same weight is identical.
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Educational estimate only — not medical advice, diagnosis or treatment. Consult a qualified clinician for health decisions.