Calculate the Basal Metabolic Rate

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Basal Metabolic Rate (BMR) Calculator

Calculate the calories your body burns at rest.

Your Basal Metabolic Rate:

0

Calories per day

Daily Calorie Estimates Based on Activity:

  • Sedentary:
  • Light Exercise:
  • Moderate Exercise:
  • Active:

Understanding Basal Metabolic Rate (BMR)

Basal Metabolic Rate, or BMR, is the total number of calories that your body needs to perform basic, life-sustaining functions. These basal functions include circulation, breathing, cell production, nutrient processing, protein synthesis, and ion transport. Calculating your BMR is the first step toward understanding your metabolism and managing your weight goals.

The Mifflin-St Jeor Equation

This calculator uses the Mifflin-St Jeor Equation, which is currently considered the most accurate formula for predicting BMR in healthy adults. The calculation works as follows:

  • For Men: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
  • For Women: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161

Why Your BMR Matters

Your BMR accounts for roughly 60% to 75% of your total daily energy expenditure (TDEE). By knowing this number, you can determine how many calories you should consume to lose, gain, or maintain your weight:

  • Weight Loss: Consume fewer calories than your TDEE (BMR + activity).
  • Weight Maintenance: Consume calories equal to your TDEE.
  • Weight Gain: Consume more calories than your TDEE.

Factors That Influence Your Metabolism

Several variables can affect your basal metabolism, including:

  • Muscle Mass: Muscle tissue burns more calories at rest than fat tissue. Increasing muscle mass increases BMR.
  • Age: BMR typically decreases as you get older due to the loss of lean muscle mass.
  • Genetics: Genetic factors play a significant role in determining your metabolic rate.
  • Hormones: Thyroid hormones, in particular, regulate the speed of your metabolism.

BMR vs. TDEE

While BMR is what you burn doing absolutely nothing, your Total Daily Energy Expenditure (TDEE) is the total calories burned including physical activity. To find your TDEE, you multiply your BMR by an activity factor (e.g., 1.2 for sedentary, 1.55 for moderate activity). This gives a more realistic picture of your daily caloric requirements.

function calculateBMR() { var age = parseFloat(document.getElementById('bmr-age').value); var weight = parseFloat(document.getElementById('bmr-weight').value); var height = parseFloat(document.getElementById('bmr-height').value); var genderElements = document.getElementsByName('gender'); var gender = 'male'; var bmr = 0; for (var i = 0; i < genderElements.length; i++) { if (genderElements[i].checked) { gender = genderElements[i].value; break; } } if (isNaN(age) || isNaN(weight) || isNaN(height) || age <= 0 || weight <= 0 || height <= 0) { alert("Please enter valid positive numbers for age, weight, and height."); return; } // Mifflin-St Jeor Equation if (gender === 'male') { bmr = (10 * weight) + (6.25 * height) – (5 * age) + 5; } else { bmr = (10 * weight) + (6.25 * height) – (5 * age) – 161; } var resultContainer = document.getElementById('bmr-result-container'); var resultValue = document.getElementById('bmr-value'); resultValue.innerText = Math.round(bmr).toLocaleString(); // Calculate activity levels (TDEE) document.getElementById('sed-cal').innerText = Math.round(bmr * 1.2).toLocaleString() + " kcal"; document.getElementById('light-cal').innerText = Math.round(bmr * 1.375).toLocaleString() + " kcal"; document.getElementById('mod-cal').innerText = Math.round(bmr * 1.55).toLocaleString() + " kcal"; document.getElementById('active-cal').innerText = Math.round(bmr * 1.725).toLocaleString() + " kcal"; resultContainer.style.display = 'block'; resultContainer.scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }

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