BMR Calculator
Find your Basal Metabolic Rate. Calories burned at rest.
What Is the BMR Calculator?
A BMR calculator estimates your basal metabolic rate, the energy your body burns simply existing: heartbeat, breathing, cell repair, brain function, and temperature regulation, all before you take a step. Enter sex, age, height, and weight and the tool applies the Mifflin St Jeor equation, the formula nutrition professionals consider among the most accurate available without lab equipment. Knowing this baseline anchors everything downstream: multiply it by activity factors to estimate total daily burn, set defensible calorie targets for fat loss without crashing metabolism assumptions, or plan weight gain surpluses. Two people with identical bodies but different ages or heights can differ by hundreds of calories per day, which is why copying a friend's diet plan rarely works.
Key Statistics
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60% to 70%
Approximate share of daily energy expenditure spent on basal metabolism
Source: Human physiology consensus estimates
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1919
Year of the original Harris Benedict equation, the historical predecessor of modern formulas
Source: American Journal of Physiology archive
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1990
Publication year of the Mifflin St Jeor equation used by this calculator
Source: American Journal of Clinical Nutrition
The Formula
Mifflin-St Jeor: Men 10xweight(kg)+6.25xheight(cm)-5xage+5. Women 10xweight+6.25xheight-5xage-161.
Worked Examples
A 35-year-old man at 5 foot 10 inches (178 cm) and 175 pounds (79 kg) has a BMR of approximately 1,765 calories per day using the Mifflin-St Jeor equation. A 30-year-old woman of identical height and weight has a BMR of roughly 1,600 calories.
Male example
- Age 35, height 180 centimeters, weight 80 kilograms
- Apply 10 times weight plus 6.25 times height minus 5 times age plus 5
- Compute 800 plus 1,125 minus 175 plus 5
BMR is about 1,755 calories per day.
Female example
- Age 30, height 165 centimeters, weight 60 kilograms
- Apply 10 times weight plus 6.25 times height minus 5 times age minus 161
- Compute 600 plus 1,031.25 minus 150 minus 161
BMR is about 1,320 calories per day.
Real World Use Cases
Setting calorie targets
Multiply BMR by an activity factor to estimate maintenance calories before cutting or bulking.
Understanding plateaus
Recalculate after losing significant weight because a smaller body burns less at rest.
Clinical nutrition planning
Dietitians anchor enteral and parenteral feeding calculations to estimated BMR.
Comparing metabolism myths
See objectively how little variation exists between similar sized people.
Expert Tips
- ✓ Never eat at or below BMR for extended periods; deficits belong somewhere between BMR and total expenditure.
- ✓ Lean mass drives most variation, so resistance training raises the ceiling better than any food choice.
- ✓ Formulas carry roughly plus or minus 10 percent error; treat results as starting points and adjust with real world data.
- ✓ Sleep deprivation and severe dieting can measurably suppress expenditure through adaptive responses.
- ✓ Weigh yourself under consistent conditions weekly and let trend lines override formula estimates.
Frequently Asked Questions
What is BMR? ▼
BMR (basal metabolic rate) is the number of calories your body burns at complete rest to keep basic functions running, like breathing, circulation, and cell repair. It is the largest share of your daily calorie burn.
How is BMR calculated? ▼
This calculator uses the Mifflin St Jeor equation, which factors in sex, age, height, and weight. For men it is 10 times weight in kg plus 6.25 times height in cm minus 5 times age plus 5. For women, the formula ends with minus 161.
What is the difference between BMR and TDEE? ▼
BMR is the calories burned at rest, while TDEE (total daily energy expenditure) adds in all your activity, exercise, and digestion. Your maintenance calories are your TDEE, which is your BMR times an activity factor.
How do I use BMR to lose weight? ▼
To lose weight, eat slightly below your total daily energy expenditure, not just below BMR. A deficit of about 500 calories per day typically leads to roughly 1 pound lost per week, since a pound of fat is about 3,500 calories.
What is a calorie deficit? ▼
A calorie deficit is eating fewer calories than your body burns. Your body then makes up the difference from stored fat, which is how weight loss happens. Keep the deficit moderate to protect muscle and energy.
What are safe calorie minimums? ▼
Common guidance warns against going below about 1,200 calories per day for women and 1,500 for men without medical supervision. Very low intakes risk nutrient deficiencies and metabolic slowdown. Consult a professional for an individual plan.
What is the difference between BMR and TDEE? ▼
BMR covers resting function only. Total daily energy expenditure multiplies BMR by an activity factor reflecting movement, exercise, and digestion.
How do I calculate my BMR? ▼
Use the Mifflin St Jeor equation: ten times weight in kilograms, plus 6.25 times height in centimeters, minus five times age in years, plus five for men or minus 161 for women.
Common Mistakes to Avoid
- ⚠ Using your BMR as your daily calorie target. A BMR of 1,500 is what your organs need at complete rest. Eating at BMR while active creates a dangerous deficit below 1,200 calories for many people. Your target should be based on TDEE, not BMR.
- ⚠ Choosing the wrong activity multiplier. Selecting "extra active" when you have a desk job and exercise 3 days per week can overestimate your TDEE by 500-800 calories per day. Be honest about your average week, not your best week.
- ⚠ Not recalculating BMR after significant weight changes. Losing 20 lb (about 9 kg) reduces your BMR by roughly 100-150 calories per day. Using your old BMR after weight loss is one reason weight loss plateaus happen.
- ⚠ Applying activity multipliers twice. If you already estimate total calories from a tracker, do not additionally inflate BMR.
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Last updated: · by CalculatorPro Tools