.heart-rate-calculator-container {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
max-width: 800px;
margin: 0 auto;
padding: 20px;
background: #fff;
color: #333;
}
.calc-box {
background-color: #f9f9f9;
border: 1px solid #e0e0e0;
border-radius: 8px;
padding: 30px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
margin-bottom: 40px;
}
.calc-title {
text-align: center;
color: #d32f2f;
margin-bottom: 25px;
font-size: 24px;
font-weight: 700;
}
.form-group {
margin-bottom: 20px;
}
.form-label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #555;
}
.form-input {
width: 100%;
padding: 12px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
transition: border-color 0.3s;
}
.form-input:focus {
border-color: #d32f2f;
outline: none;
}
.calc-btn {
display: block;
width: 100%;
background-color: #d32f2f;
color: white;
border: none;
padding: 15px;
font-size: 18px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
transition: background-color 0.3s;
}
.calc-btn:hover {
background-color: #b71c1c;
}
.result-box {
margin-top: 25px;
padding: 20px;
background-color: #ffebee;
border-radius: 4px;
border-left: 5px solid #d32f2f;
display: none;
}
.result-row {
display: flex;
justify-content: space-between;
margin-bottom: 10px;
font-size: 18px;
}
.result-label {
font-weight: 600;
}
.result-value {
font-weight: 700;
color: #d32f2f;
}
.article-content {
line-height: 1.6;
color: #444;
}
.article-content h2 {
color: #333;
margin-top: 30px;
font-size: 22px;
}
.article-content h3 {
color: #555;
font-size: 18px;
margin-top: 20px;
}
.article-content ul {
padding-left: 20px;
}
.article-content li {
margin-bottom: 10px;
}
.note {
font-size: 12px;
color: #666;
margin-top: 5px;
}
function calculateZone() {
var ageInput = document.getElementById('userAge');
var rhrInput = document.getElementById('restingHR');
var resultDiv = document.getElementById('resultDisplay');
var resMHR = document.getElementById('resMHR');
var resZone = document.getElementById('resZone');
var age = parseFloat(ageInput.value);
var rhr = parseFloat(rhrInput.value);
if (isNaN(age) || age 120) {
alert("Please enter a valid age.");
return;
}
// 1. Calculate Maximum Heart Rate (Standard Formula: 220 – Age)
var maxHeartRate = 220 – age;
var lowerBound, upperBound;
// 2. Calculate Zones
if (!isNaN(rhr) && rhr > 0 && rhr < maxHeartRate) {
// Use Karvonen Formula if RHR is provided for better accuracy
// Target HR = ((Max HR − Resting HR) × %Intensity) + Resting HR
var heartRateReserve = maxHeartRate – rhr;
// Fat burning zone typically 60% to 70%
lowerBound = Math.round((heartRateReserve * 0.60) + rhr);
upperBound = Math.round((heartRateReserve * 0.70) + rhr);
} else {
// Use Standard Percentage Method if RHR is missing
// Target HR = Max HR x %Intensity
lowerBound = Math.round(maxHeartRate * 0.60);
upperBound = Math.round(maxHeartRate * 0.70);
}
// Display Results
resMHR.innerHTML = maxHeartRate + " bpm";
resZone.innerHTML = lowerBound + " – " + upperBound + " bpm";
resultDiv.style.display = "block";
}
How to Calculate Optimal Heart Rate for Fat Burning
Finding your optimal heart rate for fat burning is one of the most effective ways to maximize the efficiency of your cardio workouts. Rather than pushing yourself to exhaustion, fat burning occurs most efficiently at a moderate intensity where your body utilizes fat stores as its primary fuel source.
The Science of the "Fat Burning Zone"
The "Fat Burning Zone" is typically defined as a heart rate intensity between 60% and 70% of your maximum heart rate. At this specific level of exertion, your body requires oxygen to generate energy (aerobic metabolism). Because fat oxidation requires oxygen, working out in this zone allows your body to burn a higher percentage of calories from fat compared to glycogen (carbohydrates).
Understanding the Formulas
This calculator utilizes two primary methods to determine your zones:
- The Standard Method (MHR): This estimates your Maximum Heart Rate (220 minus your age) and simply takes 60-70% of that number. It is a good baseline if you do not know your resting heart rate.
- The Karvonen Formula: This is the "Optimal" method used when you input your Resting Heart Rate. It accounts for your fitness level by calculating your Heart Rate Reserve (Max HR minus Resting HR). This results in a more personalized target range that grows with your fitness level.
How to Measure Your Heart Rate
To ensure you are training in the optimal zone calculated above, you can use a wearable fitness tracker, a chest strap monitor, or manually check your pulse at your wrist or neck for 15 seconds and multiply by 4.
Example Calculation
Consider a 40-year-old individual with a resting heart rate of 70 bpm using the Karvonen method:
- Max Heart Rate: 220 – 40 = 180 bpm
- Heart Rate Reserve: 180 – 70 = 110 bpm
- Lower Limit (60%): (110 × 0.60) + 70 = 136 bpm
- Upper Limit (70%): (110 × 0.70) + 70 = 147 bpm
This individual should aim to keep their heart rate between 136 and 147 bpm during sustained cardio exercise (like jogging, cycling, or brisk walking) to optimize fat oxidation.