Metabolic Age Calculator
Enter your age, sex, weight, height, and activity level to estimate your resting metabolic rate (RMR) and see how your metabolism compares to population norms for your age — your metabolic age.
Used to contextualise your metabolic rate — not included in RMR calculation
Helps refine your metabolic age estimate — muscle burns more calories at rest
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Metabolic age estimates how your resting metabolic rate compares to average values for people at different ages. If your metabolism burns calories at the rate typical of a 45-year-old but you're 38, your metabolic age is 45. The gap reflects muscle mass, activity level, sleep quality, and chronic lifestyle habits. Unlike chronological age, metabolic age is modifiable — and this calculator shows you the levers.
Example
Age: 40 | Weight: 85kg | Height: 178cm | Sex: Male Activity: sedentary | Muscle mass: average Estimated RMR: 1,780 kcal/day Population average RMR at this RMR level: age 47 Metabolic age: 47 (7 years older than chronological) Primary driver: low muscle mass + sedentary lifestyle
RMR Formula (Mifflin-St Jeor)
Men: RMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5 Women: RMR = (10 × kg) + (6.25 × cm) − (5 × age) − 161 Metabolic age = Age at which population average RMR equals your calculated RMR
What Determines Your RMR
Resting metabolic rate is set primarily by lean muscle mass (about 70%), then organ size, age, sex, and thyroid function. Fat mass contributes minimally. This is why strength training is the most powerful long-term intervention for a faster metabolism — it increases the muscle-mass component. Crash dieting does the opposite: it loses muscle alongside fat and permanently lowers RMR.
Frequently Asked Questions
Can I lower my metabolic age?
Yes. Building muscle (resistance training 2–3×/week), optimising sleep (7–9h), and maintaining a slight calorie surplus while training are the main levers.
Does eating more boost metabolism?
Slightly — the thermic effect of food and avoiding extreme restriction prevent metabolic adaptation. But this effect is small compared to muscle mass.
Why do women typically have lower RMR than men?
Men generally have more lean muscle mass per unit of body weight. When RMR is adjusted for lean mass, the gender gap largely disappears.
Is a 'younger' metabolic age always better?
Generally yes — it indicates more metabolically active tissue (muscle) and lower fat mass, both associated with better health outcomes.