.thr-calculator-container {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 20px auto;
padding: 25px;
border: 1px solid #e0e0e0;
border-radius: 12px;
background-color: #ffffff;
box-shadow: 0 4px 15px rgba(0,0,0,0.05);
}
.thr-calculator-container h2 {
color: #2c3e50;
margin-top: 0;
font-size: 24px;
border-bottom: 2px solid #3498db;
padding-bottom: 10px;
}
.thr-input-group {
margin-bottom: 20px;
}
.thr-input-group label {
display: block;
font-weight: 600;
margin-bottom: 8px;
color: #34495e;
}
.thr-input-group input {
width: 100%;
padding: 12px;
border: 1px solid #ccd1d9;
border-radius: 6px;
font-size: 16px;
box-sizing: border-box;
}
.thr-btn {
background-color: #3498db;
color: white;
padding: 14px 20px;
border: none;
border-radius: 6px;
cursor: pointer;
width: 100%;
font-size: 18px;
font-weight: bold;
transition: background-color 0.3s;
}
.thr-btn:hover {
background-color: #2980b9;
}
.thr-result {
margin-top: 25px;
padding: 20px;
background-color: #f8f9fa;
border-radius: 8px;
border-left: 5px solid #3498db;
display: none;
}
.thr-result h3 {
margin-top: 0;
color: #2c3e50;
}
.thr-metric {
font-size: 1.1em;
margin: 10px 0;
color: #444;
}
.thr-value {
font-weight: bold;
color: #e74c3c;
}
.thr-article {
margin-top: 40px;
line-height: 1.6;
color: #333;
}
.thr-article h3 {
color: #2c3e50;
margin-top: 25px;
}
.thr-table {
width: 100%;
border-collapse: collapse;
margin: 20px 0;
}
.thr-table th, .thr-table td {
border: 1px solid #ddd;
padding: 12px;
text-align: left;
}
.thr-table th {
background-color: #f2f2f2;
}
Target Heart Rate Calculator (Karvonen Formula)
Your Age (years)
Resting Heart Rate (BPM)
Measure your pulse for 60 seconds while sitting still.
Exercise Intensity (%)
Moderate: 50-70%, Vigorous: 70-85%
Calculate Target Heart Rate
Your Personalized Results
Maximum Heart Rate (MHR):
Heart Rate Reserve (HRR):
Target Heart Rate at
*Results are based on the Karvonen Formula, which accounts for your fitness level via resting heart rate.
How to Calculate Target Heart Rate During Exercise
Understanding your target heart rate (THR) is essential for maximizing the efficiency of your workouts. Whether your goal is weight loss, cardiovascular endurance, or peak athletic performance, exercising within specific "zones" ensures you are putting in the right amount of effort without overtraining.
The Karvonen Formula: A Better Way to Calculate
Many people use the simple "220 minus age" formula to find their maximum heart rate. However, fitness professionals prefer the Karvonen Formula . This method is more accurate because it incorporates your Resting Heart Rate (RHR) , which reflects your current level of cardiovascular fitness.
The math works like this:
Max Heart Rate (MHR): 220 – Your AgeHeart Rate Reserve (HRR): MHR – Resting Heart RateTarget Heart Rate: (HRR × % Intensity) + Resting Heart Rate
Heart Rate Training Zones
Zone
Intensity
Benefit
Zone 1: Very Light
50% – 60%
Recovery, warm-up, and basic health.
Zone 2: Light
60% – 70%
Fat metabolism and basic endurance.
Zone 3: Moderate
70% – 80%
Aerobic capacity and cardiovascular health.
Zone 4: Hard
80% – 90%
Increased speed and anaerobic capacity.
Zone 5: Maximum
90% – 100%
Sprint speed and peak performance.
Calculation Example
Imagine a 40-year-old individual with a resting heart rate of 70 BPM who wants to exercise at a 75% intensity (Zone 3/4 border).
MHR: 220 – 40 = 180 bpmHRR: 180 – 70 = 110 bpmTarget: (110 × 0.75) + 70 = 82.5 + 70 = 152.5 bpm
Practical Tips for Success
To get the most out of your target heart rate data:
Measure RHR accurately: Check your pulse first thing in the morning while still in bed.Use a Monitor: While manual pulse checks work, a chest strap or optical heart rate sensor provides real-time accuracy during movement.Listen to your body: Formulas provide estimates. If you feel excessively dizzy or short of breath, slow down regardless of the numbers.Consult a professional: If you are on medications (like beta-blockers) that affect heart rate, consult your doctor to set appropriate targets.
function calculateTHR() {
var age = document.getElementById('age').value;
var rhr = document.getElementById('rhr').value;
var intensity = document.getElementById('intensity').value;
if (age === "" || rhr === "" || intensity === "") {
alert("Please fill in all fields to calculate your target heart rate.");
return;
}
var ageNum = parseFloat(age);
var rhrNum = parseFloat(rhr);
var intNum = parseFloat(intensity);
if (ageNum 120 || rhrNum <= 0 || intNum 100) {
alert("Please enter valid positive numbers for all fields.");
return;
}
// Logic: Karvonen Formula
var mhr = 220 – ageNum;
var hrr = mhr – rhrNum;
if (hrr <= 0) {
alert("Resting heart rate cannot be higher than maximum heart rate. Please check your inputs.");
return;
}
var thr = (hrr * (intNum / 100)) + rhrNum;
// Display results
document.getElementById('mhrVal').innerText = Math.round(mhr);
document.getElementById('hrrVal').innerText = Math.round(hrr);
document.getElementById('intVal').innerText = intNum;
document.getElementById('thrVal').innerText = Math.round(thr);
document.getElementById('thrResult').style.display = 'block';
}