Calculating the exact number of calories burned during exercise can be complex, as it depends on numerous factors including your age, weight, sex, fitness level, and the intensity of your workout. Heart rate is a key indicator of exercise intensity. Higher heart rates generally correspond to higher calorie expenditure.
This calculator provides an estimate of calories burned based on your age, weight, the duration of your exercise, and your average heart rate during that period. It uses a simplified MET (Metabolic Equivalent of Task) value derived from heart rate to estimate calorie expenditure.
How it Works:
Age: Affects your maximum heart rate and metabolic rate.
Weight: A heavier individual will generally burn more calories than a lighter individual for the same activity.
Duration: The longer you exercise, the more calories you burn.
Heart Rate: This is the primary indicator of intensity. We use it to infer the MET value of your activity. A common approximation is that for every 10 bpm above your resting heart rate, the MET value increases. For example, a heart rate around 70-80% of your maximum is often considered vigorous.
Important Note: This calculator offers an estimation. For precise measurements, consider using a fitness tracker or consulting with a fitness professional.
function calculateCaloriesBurned() {
var age = parseFloat(document.getElementById("age").value);
var weightKg = parseFloat(document.getElementById("weightKg").value);
var durationMinutes = parseFloat(document.getElementById("durationMinutes").value);
var heartRate = parseFloat(document.getElementById("heartRate").value);
var resultElement = document.getElementById("result");
// Input validation
if (isNaN(age) || isNaN(weightKg) || isNaN(durationMinutes) || isNaN(heartRate) ||
age <= 0 || weightKg <= 0 || durationMinutes <= 0 || heartRate <= 0) {
resultElement.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
// Estimate maximum heart rate (MHR) using the Fox formula (220 – age)
var maxHeartRate = 220 – age;
// Determine approximate MET based on heart rate as a percentage of MHR
// These are general ranges and can vary significantly
var metValue;
var heartRatePercentage = (heartRate / maxHeartRate) * 100;
if (heartRatePercentage = 50 && heartRatePercentage = 60 && heartRatePercentage = 70 && heartRatePercentage = 80 && heartRatePercentage < 90) { // 80-89% MHR (Vigorous Activity)
metValue = 7.0;
} else { // 90%+ MHR (Very Vigorous Activity)
metValue = 8.5;
}
// Calorie burn formula: Calories = MET * weight (kg) * duration (hours)
var durationHours = durationMinutes / 60;
var caloriesBurned = metValue * weightKg * durationHours;
resultElement.innerHTML = "Estimated Calories Burned: " + caloriesBurned.toFixed(2) + " kcal";
}