Find out how fast your metabolism is, how it compares to average for your age, and how it will change over time.
Calculate My Metabolism ↓Uses the Mifflin-St Jeor formula — the most accurate BMR equation for healthy adults.
After age 30, adults lose 3–8% of muscle mass per decade without resistance training. Since muscle burns more calories than fat, this directly reduces BMR.
Declining levels of testosterone (men) and oestrogen (women) with age reduce anabolic drive, making it harder to maintain muscle mass and metabolic rate.
NEAT (non-exercise movement) tends to decrease with age — less spontaneous movement, walking, and fidgeting. This can reduce total daily calorie burn by 200–400 kcal.
Resistance training 2–4 times per week, adequate protein intake (1.6–2.2g/kg), staying physically active, and good sleep are the most effective interventions to maintain metabolic rate with age.
This calculator uses the Mifflin-St Jeor equation, published in 1990, which is generally considered the most accurate formula available for estimating Basal Metabolic Rate (BMR) — the calories your body burns at complete rest just to keep vital functions running (breathing, circulation, cell repair). Independent validation studies have found it more accurate than older formulas like Harris-Benedict for most modern populations. Your Total Daily Energy Expenditure (TDEE) is then calculated by multiplying BMR by an activity multiplier that accounts for exercise and daily movement.
Even the best formulas carry a margin of error of around 10% for the general population, since BMR is also influenced by genetics, muscle mass, thyroid function, and other factors that a simple age/weight/height formula can't capture. Use the result as a starting point: track your actual weight trend against your intake for 2-3 weeks and adjust the number up or down by 100-150 kcal based on real-world results rather than treating the calculator's output as exact.
Get your full daily calorie and macro targets.
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