Enter your details above to see your personalized heart rate zone based on the Karvonen Formula.
function calculateTargetHeartRate() {
var age = document.getElementById('thr_age').value;
var restingHR = document.getElementById('thr_resting').value;
var intensity = document.getElementById('thr_intensity').value;
var resultDiv = document.getElementById('thr-result-container');
var displayValue = document.getElementById('thr_final_result');
var explanation = document.getElementById('thr_explanation');
if (age === "" || restingHR === "") {
alert("Please enter both your age and resting heart rate.");
return;
}
var ageNum = parseInt(age);
var restingNum = parseInt(restingHR);
var intensityNum = parseFloat(intensity);
if (ageNum 115) {
alert("Please enter a valid age.");
return;
}
// Max Heart Rate (MHR) – Standard Formula
var maxHR = 220 – ageNum;
// Heart Rate Reserve (HRR) – Karvonen Formula
var hrr = maxHR – restingNum;
// Target Heart Rate = (HRR * Intensity%) + Resting HR
var lowerIntensity = intensityNum;
var upperIntensity = intensityNum + 0.10;
var targetLower = Math.round((hrr * lowerIntensity) + restingNum);
var targetUpper = Math.round((hrr * upperIntensity) + restingNum);
resultDiv.style.display = "block";
displayValue.innerHTML = targetLower + " – " + targetUpper + " BPM";
explanation.innerHTML = "Max Heart Rate: " + maxHR + " BPM" +
"Heart Rate Reserve: " + hrr + " BPM" +
"At your current age and fitness level, exercising in this range helps optimize your cardiovascular results for the selected intensity.";
}
Understanding How to Calculate Your Target Heart Rate
Whether you are a seasoned athlete or just starting your fitness journey, knowing your target heart rate (THR) is essential for safe and effective training. Exercising at the right intensity ensures you are pushing your cardiovascular system enough to see improvements without overexerting yourself.
What is Target Heart Rate?
Target heart rate is a range of beats per minute (BPM) that represents the ideal intensity level for your heart during physical activity. This range varies based on your age, fitness level, and specific health goals, such as fat loss or improved athletic performance.
The Karvonen Formula Explained
The calculator above uses the Karvonen Formula, which is widely considered more accurate than simple percentage-based calculations because it accounts for your Resting Heart Rate (RHR).
Maximum Heart Rate (MHR): The highest number of times your heart can safely beat in one minute. A common estimate is 220 minus your age.
Resting Heart Rate (RHR): The number of times your heart beats per minute while at complete rest (best measured right after waking up).
Heart Rate Reserve (HRR): The difference between your MHR and RHR. This represents the "cushion" of heartbeats you have available for exercise.
Exercise Intensity Zones
Depending on your goals, you should aim for different intensity percentages:
Moderate Activity (50-60%): Ideal for beginners, warm-ups, and active recovery.
Weight Management (60-70%): Often called the "fat-burning zone," this intensity is sustainable for longer durations.
Aerobic Endurance (70-80%): Improves cardiovascular health and lung capacity; the "sweet spot" for most fitness enthusiasts.
Anaerobic/Performance (80-90%): Increases your lactate threshold and improves speed and power.
Maximum Effort (90-100%): Reserved for high-intensity interval training (HIIT) and short sprints.
Example Calculation
If you are 30 years old with a resting heart rate of 60 BPM and want to exercise at 70% intensity:
Max HR = 220 – 30 = 190 BPM.
Heart Rate Reserve = 190 – 60 = 130 BPM.
Target = (130 * 0.70) + 60 = 151 BPM.
In this example, 151 BPM would be the lower end of your 70-80% aerobic training zone.
Tips for Success
Always consult with a healthcare provider before starting a new vigorous exercise program, especially if you have underlying health conditions or are taking medications that affect heart rate (such as beta-blockers). For the most accurate tracking, consider using a wearable chest strap or a reliable fitness watch during your workouts.