Heart Rate Based Calorie Burn Calculator

Estimating calorie expenditure during exercise is crucial for managing weight loss, fitness goals, and nutritional intake. While general estimates based on activity type exist, using your actual heart rate during exercise provides a significantly more accurate calculation of energy expenditure.

This calculator utilizes the widely respected Keytel Formula published in the Journal of Sports Sciences. By inputting your personal metrics and average heart rate during a workout session, you can get a personalized estimate of kilocalories (kcal) burned.

Calculate Your Workout Energy Expenditure

Male Female

Enter the average beats per minute sustained during the activity.

Estimated Expenditure:

How Heart Rate Determination Works

The relationship between heart rate and oxygen consumption (VO2) is relatively linear during aerobic exercise. Since oxygen consumption is directly tied to energy expenditure, knowing your heart rate allows for a much more precise calculation than simply guessing based on the type of activity (e.g., "jogging" vs. "running").

For example, a 30-year-old male weighing 80kg running for 60 minutes might burn vastly different calorie amounts depending on intensity. If his average heart rate was 130 BPM (moderate effort), he might burn around 600 kcal. If his average was 165 BPM (high intensity), that number could jump closer to 950 kcal. Heart rate data is essential for capturing this difference.

Factors Influencing the Calculation

• Gender: Men generally have a higher proportion of muscle mass and lower body fat than women, leading to a slightly higher metabolic rate during exercise. The formulas adjust for this biological difference.
• Weight: Moving a heavier body requires more energy. Therefore, calorie burn increases with body weight.
• Age: Maximum heart rate typically decreases with age, and metabolic efficiency changes. The formula accounts for these age-related shifts.
• Heart Rate Intensity: This is the most critical variable. A higher heart rate indicates greater cardiovascular demand and higher energy expenditure per minute.

Limitations of Heart Rate Formulas

While highly useful, keep in mind these are estimates. Factors like individual fitness levels (VO2 max), ambient temperature, stimulants (like caffeine), and stress can elevate heart rate without a proportional increase in calorie burn. This calculator is best suited for steady-state aerobic activities like running, cycling, or rowing, rather than anaerobic activities like heavy weightlifting.

function calculateCaloriesBurned() { // 1. Get input values var genderSelect = document.getElementById('gender'); var gender = genderSelect.options[genderSelect.selectedIndex].value; var ageInput = document.getElementById('age').value; var weightInput = document.getElementById('weight').value; var heartRateInput = document.getElementById('heartRate').value; var durationInput = document.getElementById('duration').value; // Get weight unit radio selection var weightUnitRadios = document.getElementsByName('weightUnit'); var weightUnit = 'kg'; // default for (var i = 0; i < weightUnitRadios.length; i++) { if (weightUnitRadios[i].checked) { weightUnit = weightUnitRadios[i].value; break; } } // 2. Validate inputs var age = parseFloat(ageInput); var weight = parseFloat(weightInput); var hr = parseFloat(heartRateInput); var duration = parseFloat(durationInput); if (isNaN(age) || age <= 0 || isNaN(weight) || weight <= 0 || isNaN(hr) || hr <= 0 || isNaN(duration) || duration <= 0) { document.getElementById('resultContainer').style.display = 'block'; document.getElementById('result').innerHTML = 'Please enter valid, positive numbers for all fields.'; return; } // 3. Convert weight to kg if necessary (Keytel formula uses kg) var weightInKg = weight; if (weightUnit === 'lbs') { weightInKg = weight * 0.45359237; } // 4. Calculate Calories per minute using the Keytel formula // Note: The formula results in kJ/min, dividing by 4.184 converts to kcal/min. var caloriesPerMinute = 0; if (gender === 'male') { // Male Formula: C/min = (-55.0969 + (0.6309 x HR) + (0.1988 x W) + (0.2017 x A)) / 4.184 caloriesPerMinute = (-55.0969 + (0.6309 * hr) + (0.1988 * weightInKg) + (0.2017 * age)) / 4.184; } else { // Female Formula: C/min = (-20.4022 + (0.4472 x HR) – (0.1263 x W) + (0.074 x A)) / 4.184 caloriesPerMinute = (-20.4022 + (0.4472 * hr) – (0.1263 * weightInKg) + (0.074 * age)) / 4.184; } // Ensure result isn't negative in extreme edge cases (unlikely with valid HR inputs) if (caloriesPerMinute < 0) { caloriesPerMinute = 0; } // 5. Calculate total for duration var totalCalories = caloriesPerMinute * duration; // 6. Display Result document.getElementById('resultContainer').style.display = 'block'; document.getElementById('result').innerHTML = totalCalories.toFixed(0) + ' kcal'; }