BMR Calculator
Calculate Your Basal Metabolic Rate (BMR)
BMR basics
What Is BMR?
BMR stands for Basal Metabolic Rate. It is the estimated number of calories your body uses at rest to keep essential functions running.
Getting started
How to Use This BMR Calculator
Use BMR as your baseline resting energy estimate, then combine it with activity level to estimate total daily needs.
- 1
Choose units
Select metric or US standard units.
- 2
Enter body details
Choose sex, age, height, and weight for Mifflin-St Jeor or Harris-Benedict.
- 3
Choose a formula
Use Mifflin-St Jeor by default or compare with Harris-Benedict and Katch-McArdle.
- 4
Calculate BMR
Review your baseline resting calorie burn in the results tab.
- 5
Use with activity level
Multiply BMR by an activity factor to estimate TDEE for nutrition planning.
The math
Metabolic Rate Formulas
This calculator can compare Mifflin-St Jeor, Revised Harris-Benedict, and Katch-McArdle formulas.
| Formula | Equation |
|---|---|
| Mifflin-St Jeor | Men: 10W + 6.25H - 5A + 5; Women: 10W + 6.25H - 5A - 161 |
| Revised Harris-Benedict | Men: 13.397W + 4.799H - 5.677A + 88.362; Women: 9.247W + 3.098H - 4.330A + 447.593 |
| Katch-McArdle | 370 + 21.6 × Lean Body Mass |
TDEE relationship
BMR is the resting baseline; TDEE estimates full-day calorie burn.
Example
BMR Calculation Example
This example shows how the Mifflin-St Jeor formula calculates a resting calorie estimate.
| Step | Value |
|---|---|
| Example person | 30-year-old male, 75 kg, 175 cm |
| Formula | 10(75) + 6.25(175) - 5(30) + 5 |
| Result | 1,699 calories/day |
| Meaning | This is the estimated baseline energy needed at rest. |
Energy terms
BMR vs TDEE vs RMR
These terms are close, but they are not identical. Understanding the difference makes calorie planning easier.
- BMR vs TDEE
- BMR is your minimum resting energy floor. TDEE includes BMR plus walking, workouts, digestion, and normal daily movement.
- BMR vs RMR
- BMR is measured under stricter lab conditions, while RMR is measured under more practical resting conditions. For everyday tracking, they are often close enough to use similarly.
BMR drivers
What Affects BMR?
Your resting metabolic rate is individualized and changes with body size, lean mass, age, and health context.
- Age and aging
- BMR often declines gradually with age as muscle mass and activity patterns change.
- Biological sex
- Men often have higher BMR because they carry more lean mass on average.
- Height, frame, and current weight
- Larger bodies require more baseline energy to maintain vital functions.
- Lean muscle mass
- Muscle is metabolically active tissue and raises resting energy demand.
- Hormones and health status
- Thyroid function, medications, illness, and metabolic conditions can shift resting needs.
- Diet history
- Severe dieting can reduce energy expenditure through metabolic adaptation.
Practical improvement
Can You Increase BMR?
You cannot rewrite genetics, but building and preserving lean tissue can support a higher resting energy demand.
- Strength training regularly
- Muscle burns more calories than fat even at rest.
- Consume adequate protein
- Protein supports tissue repair, muscle retention, and higher thermic effect.
- Avoid extreme crash dieting
- Severe deficits can prompt your body to down-regulate BMR.
Clinical limits
Accuracy and Limitations
BMR calculations provide scientific estimates. They can overestimate or underestimate needs for some people.
Next checks
Use BMR with Other Calculators
BMR is most useful when paired with TDEE, calories, macros, BMI, body fat, and ideal weight estimates.
Frequently Asked Questions
BMR stands for Basal Metabolic Rate — the number of calories your body burns at complete rest to keep essential systems running (heart, lungs, brain, cell repair). Roughly 60–75 percent of the calories you burn each day come from your BMR.
RMR (Resting Metabolic Rate) is measured under slightly less strict conditions than BMR — usually after a few hours of rest rather than overnight fasting. The two values are typically within 5–10 percent of each other and are often used interchangeably in everyday fitness planning.
Build more lean muscle mass through resistance training (muscle burns more calories at rest than fat), eat enough protein, stay hydrated, sleep 7–9 hours per night, and avoid prolonged crash diets that drop BMR through metabolic adaptation.
Adults lose 3–8 percent of muscle mass per decade after age 30, and muscle is metabolically active tissue. Hormonal changes and reduced physical activity compound the drop. Resistance training and adequate protein largely offset this decline.
Average BMR for an adult woman is roughly 1,200–1,500 cal/day and for an adult man 1,500–1,900 cal/day, but it scales heavily with body size and muscle mass. There is no single 'good' number — what matters is matching your total intake to your TDEE.
The American Dietetic Association rates Mifflin-St Jeor as the most accurate predictive formula for healthy adults, typically within 10 percent of indirect calorimetry measurements. It outperforms the older Harris-Benedict equation for most populations.
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