Basal Metabolic Rate Calculator

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Basal Metabolic Rate (BMR) Calculator
Mifflin-St Jeor Equation (Recommended)Revised Harris-Benedict Equation
MaleFemale
Calculation Results:
— kcal/day
function calculateBMR(){var gender=document.getElementById('gender').value;var age=parseFloat(document.getElementById('age').value);var weight=parseFloat(document.getElementById('weight').value);var height=parseFloat(document.getElementById('height').value);var formula=document.getElementById('formula_type').value;var showSteps=document.getElementById('steps').checked;if(isNaN(age)||isNaN(weight)||isNaN(height)){alert('Please enter valid numeric values for age, weight, and height.');return;}var bmr=0;if(formula==='mifflin'){if(gender==='male'){bmr=(10*weight)+(6.25*height)-(5*age)+5;}else{bmr=(10*weight)+(6.25*height)-(5*age)-161;}}else{if(gender==='male'){bmr=88.362+(13.397*weight)+(4.799*height)-(5.677*age);}else{bmr=447.593+(9.247*weight)+(3.098*height)-(4.330*age);}}document.getElementById('resultValue').innerHTML=Math.round(bmr).toLocaleString();var stepsBox=document.getElementById('stepResults');if(showSteps){var tdeeTable='

Total Daily Energy Expenditure (TDEE) based on activity:

Sedentary (Little to no exercise)'+Math.round(bmr*1.2).toLocaleString()+' kcal
Lightly Active (1-3 days/week)'+Math.round(bmr*1.375).toLocaleString()+' kcal
Moderately Active (3-5 days/week)'+Math.round(bmr*1.55).toLocaleString()+' kcal
Very Active (6-7 days/week)'+Math.round(bmr*1.725).toLocaleString()+' kcal
Extra Active (Physical job/2x training)'+Math.round(bmr*1.9).toLocaleString()+' kcal
';stepsBox.innerHTML=tdeeTable;stepsBox.style.display='block';}else{stepsBox.style.display='none';}}

Calculator Use

This basal metabolic rate calculator is designed to estimate the number of calories your body burns at rest. Your Basal Metabolic Rate (BMR) represents the energy required to maintain vital functions, such as breathing, circulation, cell production, and nutrient processing, while the body is in a neutral temperate environment and a post-absorptive state.

By using this tool, you can establish a baseline for your daily caloric needs. From there, you can adjust your intake based on your activity level to lose, maintain, or gain weight.

Biological Sex
Men generally have a higher BMR than women due to higher muscle mass-to-fat ratios.
Age
BMR typically decreases as you age because lean muscle mass tends to diminish over time.
Weight and Height
Larger bodies require more energy to maintain basic metabolic processes.

How It Works

The basal metabolic rate calculator uses two primary formulas: the Mifflin-St Jeor Equation and the Revised Harris-Benedict Equation. The Mifflin-St Jeor version is currently considered the most accurate for the general population by most health professionals.

Mifflin-St Jeor Formula:

Men: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
  • Weight: Measured in kilograms (1 kg = 2.2 lbs).
  • Height: Measured in centimeters (1 inch = 2.54 cm).
  • Age: Measured in years.
  • Constants: The +5 (male) and -161 (female) account for physiological differences in muscle density.

Calculation Example

Example: A 35-year-old male weighing 85 kg (approx. 187 lbs) and standing 180 cm tall (approx. 5'11").

Step-by-step solution (Mifflin-St Jeor):

  1. Weight component: 10 × 85 = 850
  2. Height component: 6.25 × 180 = 1,125
  3. Age component: 5 × 35 = 175
  4. Formula: 850 + 1,125 – 175 + 5
  5. Result = 1,805 calories per day

This means he would burn 1,805 calories if he stayed in bed all day doing absolutely nothing.

Common Questions

What is the difference between BMR and RMR?

Basal Metabolic Rate (BMR) is measured under very restrictive conditions (dark room, fasted state, waking up). Resting Metabolic Rate (RMR) is slightly less restrictive and usually includes the energy used for very light movement and digestion, making it typically about 10% higher than BMR.

How many calories should I eat to lose weight?

To lose weight, you need to calculate your TDEE (Total Daily Energy Expenditure) by multiplying your BMR by your activity factor. Subtracting 500 calories from your TDEE daily typically results in about 1 lb (0.45 kg) of weight loss per week.

Can I increase my BMR?

Yes. While you cannot change your age or height, you can increase your BMR by increasing lean muscle mass through strength training. Muscle tissue requires more energy to maintain than fat tissue, even at rest.

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