Heart Rate Calculator by Age and Weight

Moderate (50-60%) Aerobic (70-80%) High Intensity (80-90%) Maximum Effort (90-100%)

Your Results

Max Heart Rate (MHR) – BPM

Target Heart Rate – BPM

Fat Burn Zone (60-70%) – BPM

Est. Calories/Hr (at Intensity) – kcal

function calculateHeartRate() { var age = parseFloat(document.getElementById('hr_age').value); var weight = parseFloat(document.getElementById('hr_weight').value); var restingHR = parseFloat(document.getElementById('hr_resting').value); var intensity = parseFloat(document.getElementById('hr_intensity').value); if (isNaN(age) || isNaN(weight) || isNaN(restingHR) || age <= 0 || weight <= 0) { alert("Please enter valid numbers for age, weight, and resting heart rate."); return; } // Max Heart Rate (Fox Formula: 220 – age) var mhr = 220 – age; // Heart Rate Reserve (Karvonen Formula) var hrr = mhr – restingHR; // Target Heart Rate based on selected intensity var targetHR = Math.round((hrr * intensity) + restingHR); // Fat Burn Zone (standard 60-70%) var fatBurnMin = Math.round((hrr * 0.6) + restingHR); var fatBurnMax = Math.round((hrr * 0.7) + restingHR); // Calorie estimation (Generic MET based estimation using intensity) // MET values roughly: Moderate: 4.5, Aerobic: 7, High: 10, Max: 13 var met = 0; if(intensity == 0.5) met = 4.5; else if(intensity == 0.7) met = 7.5; else if(intensity == 0.85) met = 10.5; else met = 14; var caloriesPerHour = Math.round(met * 3.5 * weight / 200 * 60); // Display Results document.getElementById('hr_results').style.display = 'block'; document.getElementById('res_mhr').innerText = mhr; document.getElementById('res_thr').innerText = targetHR; document.getElementById('res_fatburn').innerText = fatBurnMin + " – " + fatBurnMax; document.getElementById('res_calories').innerText = caloriesPerHour; }

Understanding Your Heart Rate Zones

Using a heart rate calculator by age and weight is one of the most effective ways to optimize your cardiovascular training. By identifying your specific heart rate zones, you can tailor your workouts to burn fat, build endurance, or increase peak athletic performance.

1. Maximum Heart Rate (MHR)

Your Maximum Heart Rate is the highest number of beats per minute (BPM) your heart can safely reach during all-out exertion. While the "220 minus age" formula is the standard, variables like fitness level and genetics can influence this number.

2. Target Heart Rate (The Karvonen Formula)

This calculator uses the Karvonen Formula, which is more accurate than simple percentages because it factors in your Resting Heart Rate (RHR). This accounts for your current cardiovascular fitness level—athletes typically have a lower RHR, meaning they have a larger "Heart Rate Reserve" to utilize during exercise.

3. Weight and Calories Burned

While weight doesn't change your maximum heart rate capacity, it significantly impacts how many calories you burn during a workout. A heavier individual requires more energy to move, resulting in a higher caloric expenditure at the same heart rate intensity compared to a lighter person.

Zone	Intensity	Benefit
Fat Burn	60-70%	Weight management and basic endurance.
Aerobic	70-80%	Improved cardiovascular health and lung capacity.
Anaerobic	80-90%	Increased lactic acid tolerance and speed.

Heart Rate Calculation Example

If you are 40 years old with a resting heart rate of 70 BPM:

• MHR: 220 – 40 = 180 BPM
• HR Reserve: 180 – 70 = 110 BPM
• 70% Intensity: (110 * 0.70) + 70 = 147 BPM

Disclaimer: Always consult with a physician before starting a new high-intensity exercise program, especially if you have pre-existing heart conditions.