How to Calculate Heart Rate During Exercise

Target Heart Rate Calculator

50% – Very Light (Warm up) 60% – Light (Fat Burn) 70% – Moderate (Aerobic/Cardio) 80% – Hard (Anaerobic) 90% – Maximum Effort (VO2 Max)

Your Results

Max Heart Rate

0

BPM

Heart Rate Reserve

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BPM

Target Heart Rate

0

BPM

function calculateExerciseHR() { var age = parseFloat(document.getElementById('userAge').value); var rhr = parseFloat(document.getElementById('restingHR').value); var intensity = parseFloat(document.getElementById('intensityLevel').value) / 100; if (isNaN(age) || isNaN(rhr) || age <= 0 || rhr <= 0) { alert("Please enter valid numbers for age and resting heart rate."); return; } // MHR Formula: 220 – Age var mhr = 220 – age; // HRR Formula: Max Heart Rate – Resting Heart Rate var hrr = mhr – rhr; // Karvonen Formula: (HRR * Intensity) + RHR var thr = (hrr * intensity) + rhr; document.getElementById('mhr-display').innerText = Math.round(mhr); document.getElementById('hrr-display').innerText = Math.round(hrr); document.getElementById('thr-display').innerText = Math.round(thr); document.getElementById('hr-results').style.display = 'block'; }

How to Calculate Heart Rate During Exercise

Understanding your exercise intensity is crucial for achieving fitness goals, whether you are training for a marathon or trying to lose weight. The most accurate way to measure this is by calculating your Target Heart Rate (THR) using the Karvonen Formula.

The Science Behind the Math

The Karvonen Formula is widely considered more accurate than simply taking a percentage of your Maximum Heart Rate because it factors in your Resting Heart Rate (RHR). This accounts for your current fitness level.

• Maximum Heart Rate (MHR): The highest number of beats per minute your heart can safely pump under stress. General formula: 220 – Age.
• Heart Rate Reserve (HRR): The difference between your maximum heart rate and your resting heart rate. This represents the range of beats available for exercise.
• Intensity Level: The percentage of effort you want to exert (e.g., 60% for fat burning, 80% for aerobic capacity).

Exercise Intensity Zones

Zone	Intensity	Goal
Fat Burn	60% – 70%	Weight loss and endurance
Aerobic (Cardio)	70% – 80%	Improving cardiovascular fitness
Anaerobic	80% – 90%	High-intensity speed and power

Example Calculation

If you are 40 years old with a resting heart rate of 70 BPM and want to exercise at 70% intensity:

1. Max HR: 220 – 40 = 180 BPM
2. HR Reserve: 180 – 70 = 110 BPM
3. Target HR: (110 x 0.70) + 70 = 147 BPM

In this scenario, your heart rate should stay around 147 beats per minute during your workout to maintain moderate aerobic intensity.

How to Measure Your Heart Rate

To use this calculator effectively, you need an accurate Resting Heart Rate. The best time to measure RHR is first thing in the morning before you get out of bed. Place two fingers on your wrist (radial pulse) or neck (carotid pulse) and count the beats for 60 seconds.

Important Safety Note: Consult with a physician before starting any new high-intensity exercise program, especially if you have a history of heart conditions or are taking medication that affects heart rate (like beta-blockers).