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Resting Metabolic Rate (RMR) Calculator

Find out exactly how many calories your body burns at rest. This advanced calculator adjusts for lean body mass, sleep deprivation, stress, and diet-induced metabolic slowdown.

Unit System
Biological Sex
lbs
Height
ft
in

Enables the Cunningham formula — far more accurate for athletes. Don't know? Body Fat Calculator →

Advanced Lifestyle Adjustments (optional)

Raise Your RMR

  • • Build muscle — each kg of muscle burns ~13 extra kcal/day at rest
  • • Eat enough protein — it preserves lean mass while cutting
  • • Sleep 7–9 hours — poor sleep can blunt metabolism
  • • Don't crash-diet — very low intake suppresses RMR

Estimate your full daily burn: TDEE Calculator →

What Is Resting Metabolic Rate (RMR)?

Resting Metabolic Rate is the number of calories your body burns at complete rest — just keeping your heart beating, lungs breathing, brain working, and cells repairing. It is measured in a relaxed, non-fasted state and typically accounts for 60–75% of your total daily calorie burn.

Because RMR powers the majority of your energy expenditure, it is the single most important number for setting accurate calorie targets. Small changes in RMR translate into large differences in weekly calorie intake — which is why accurate formulas and real-world lifestyle adjustments matter.

BMR vs RMR: What's the Difference?

BMR (Basal Metabolic Rate) is measured under strict laboratory conditions: lying still, after 8 hours of sleep, and fasting for 12 hours. RMR (Resting Metabolic Rate) is measured under more realistic, less strict conditions and runs about 10% higher than true BMR.

For everyday use, RMR is the more practical number — it matches how you actually live. This calculator reports your RMR as the primary figure and shows your approximate BMR equivalent alongside it.

Which RMR Formula Should You Trust?

FormulaBest ForAccuracy
Mifflin-St JeorGeneral population±10%
CunninghamAthletes, high muscle massBest for lean individuals
OwenWeight-stable adultsSimple weight-based
Harris-Benedict (Rev.)Classic referenceTends to over-estimate ~5%

The Mifflin-St Jeor equation (1990) is the clinical standard for healthy adults. The Cunningham equation (1991) is more accurate for athletic individuals because it is built on lean body mass, which is why entering your body fat % unlocks it.

How to Increase Your RMR

  • Build muscle — muscle tissue burns ~3× more calories at rest than fat. Resistance training is the most reliable RMR booster.
  • Eat enough protein — protein has the highest thermic effect of food and supports muscle retention during a deficit.
  • Prioritize sleep — poor sleep elevates cortisol and disrupts leptin/ghrelin, lowering metabolic efficiency.
  • Take diet breaks — after 3-6+ months of cutting, eat at maintenance for 1-2 weeks to reverse metabolic adaptation.
  • Manage stress — chronic cortisol suppresses thyroid function and promotes muscle breakdown.

Frequently Asked Questions

What is the difference between BMR and RMR?
Basal Metabolic Rate (BMR) is measured under strict laboratory conditions (completely rested, 8 hours sleep, 12 hours fasting). Resting Metabolic Rate (RMR) is measured under less strict conditions and is typically ~10% higher. For everyday practical use, RMR is a more realistic measure of resting burn.
Which RMR formula is best?
Mifflin-St Jeor is the gold standard for the general population. If you are very muscular or athletic, the Cunningham equation is much more accurate because it calculates calories based on Lean Body Mass rather than total body weight.
Why is my metabolism slowing down?
Metabolic rate drops due to age, loss of muscle mass, prolonged caloric restriction (dieting), poor sleep, chronic stress, or thyroid issues. You can raise your RMR by strength training to build muscle, eating sufficient protein, prioritizing sleep, and taking diet breaks to reverse metabolic adaptation.
How can I increase my RMR?
Building muscle is the most reliable way to increase RMR, as muscle tissue burns roughly 3× more calories at rest than fat tissue. Prioritizing sleep, managing stress, eating sufficient protein, and occasionally eating at maintenance (diet breaks) all help prevent and reverse metabolic slowdown.
What is the Cunningham formula and who should use it?
The Cunningham equation (1991) estimates RMR from lean body mass (LBM): RMR = 500 + 22 × LBM in kg. It is the most accurate formula for athletes and muscular individuals because it accounts for metabolically active muscle tissue. It requires knowing your body fat percentage.
Why did you add lifestyle adjustments?
Metabolism isn't a static number. Chronic stress, poor sleep, and prolonged dieting (caloric restriction) actively down-regulate your metabolism as an evolutionary survival mechanism. This calculator models those real-world adaptations so your estimate reflects your actual lifestyle.

Also Try These Free Calculators

BMR Calculator

See your basal metabolic rate with 4 scientific formulas.

TDEE Calculator

Find your full daily maintenance calories with activity.

Macro Calculator

Split your maintenance calories into protein, carb, fat targets.

Calorie Deficit Calculator

Turn your RMR into a safe, sustainable weight-loss plan.