Loading…
Estimate basal metabolic rate — calories burned at complete rest.
Estimate basal metabolic rate — calories burned at complete rest.
Enter values above and click Calculate — results will appear here with the formula explained.
Basal metabolic rate is your body's idle power draw: energy spent keeping the heart beating, lungs breathing and brain running before any movement. It typically accounts for 60–75% of total daily expenditure — meaning most of your calories burn while you sleep, sit and exist, not while you exercise. This single fact reframes weight management: protecting metabolic rate matters more than any single workout.
The Mifflin-St Jeor equation is the current standard estimate, outperforming the older Harris-Benedict formulas against measured values. Still, individual metabolism varies around any prediction — real-world measurement (indirect calorimetry) can deviate by 10% or more either way. Genetics, thyroid function, medications, muscle mass and dieting history all shift the number; formulas give the population-center estimate, and your body supplies the error bar.
Muscle is the main lever you control: each kilogram of lean mass burns roughly 13–15 kcal/day at rest versus ~4–5 for fat, and strength training preserves it during weight loss. Crash diets sacrifice disproportionate muscle — studies show up to 25–30% of rapid loss can be lean mass — which lowers BMR and engineers the rebound. Losing slowly with protein plus resistance training defends the metabolic floor this calculator reports.
Age-related BMR decline (~1–2% per decade after 30–40, accelerating later) is mostly muscle loss in disguise, not an inevitable metabolic curse. Active adults who strength-train hold far steadier numbers than sedentary peers; the 'metabolism slows at 40' story is largely sarcopenia with a PR team. Use this calculator's output as the baseline to defend, not an excuse to accept.
Eating below BMR chronically is where physiology protests: hormonal disruption (thyroid down-regulation, leptin/ghrelin shifts driving hunger), nutrient shortfalls, hair loss, fatigue and stalled loss via adaptive thermogenesis. BMR is a floor for planning, not a target — total needs (see TDEE) sit hundreds of calories above it, and deficits should come off TDEE, never dig under BMR without medical supervision.
Recheck BMR quarterly during any body-composition journey: every 5 kg lost trims roughly 50–70 kcal from the estimate, and recomposition (same weight, more muscle) nudges it upward. Stale numbers silently erase deficits — the plateau blamed on 'broken metabolism' is usually just an outdated BMR multiplied by an optimistic activity factor.
Estimate basal metabolic rate — calories burned at complete rest. Formula: Mifflin-St Jeor: BMR = 10·kg + 6.25·cm − 5·age + (male: +5 | female: −161).
Basal metabolic rate is your body's idle power draw: energy spent keeping the heart beating, lungs breathing and brain running before any movement. It typically accounts for 60–75% of total daily expenditure — meaning most of your calories burn while you sleep, sit and exist, not while you exercise. This single fact reframes weight management: protecting metabolic rate matters more than any single workout.
The Mifflin-St Jeor equation is the current standard estimate, outperforming the older Harris-Benedict formulas against measured values. Still, individual metabolism varies around any prediction — real-world measurement (indirect calorimetry) can deviate by 10% or more either way. Genetics, thyroid function, medications, muscle mass and dieting history all shift the number; formulas give the population-center estimate, and your body supplies the error bar.
Muscle is the main lever you control: each kilogram of lean mass burns roughly 13–15 kcal/day at rest versus ~4–5 for fat, and strength training preserves it during weight loss. Crash diets sacrifice disproportionate muscle — studies show up to 25–30% of rapid loss can be lean mass — which lowers BMR and engineers the rebound. Losing slowly with protein plus resistance training defends the metabolic floor this calculator reports.
Age-related BMR decline (~1–2% per decade after 30–40, accelerating later) is mostly muscle loss in disguise, not an inevitable metabolic curse. Active adults who strength-train hold far steadier numbers than sedentary peers; the 'metabolism slows at 40' story is largely sarcopenia with a PR team. Use this calculator's output as the baseline to defend, not an excuse to accept.
Eating below BMR chronically is where physiology protests: hormonal disruption (thyroid down-regulation, leptin/ghrelin shifts driving hunger), nutrient shortfalls, hair loss, fatigue and stalled loss via adaptive thermogenesis. BMR is a floor for planning, not a target — total needs (see TDEE) sit hundreds of calories above it, and deficits should come off TDEE, never dig under BMR without medical supervision.
Recheck BMR quarterly during any body-composition journey: every 5 kg lost trims roughly 50–70 kcal from the estimate, and recomposition (same weight, more muscle) nudges it upward. Stale numbers silently erase deficits — the plateau blamed on 'broken metabolism' is usually just an outdated BMR multiplied by an optimistic activity factor.
A 32-year-old male at 75 kg and 178 cm: 750 + 1112.5 − 160 + 5 ≈ 1,708 kcal burned per day at complete rest. After losing 10 kg (65 kg, same height/age): BMR falls to ~1,608 — 100 kcal less daily, which is why the same diet 'stops working' and needs recalibration, not abandonment.
Last reviewed: September 2026 · Report an error