.calculator-container {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
max-width: 800px;
margin: 0 auto;
padding: 20px;
background-color: #f9f9f9;
border-radius: 8px;
box-shadow: 0 4px 10px rgba(0,0,0,0.05);
}
.calc-box {
background: #ffffff;
padding: 30px;
border-radius: 8px;
border: 1px solid #e0e0e0;
margin-bottom: 40px;
}
.calc-row {
margin-bottom: 20px;
}
.calc-row label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #333;
}
.calc-row input {
width: 100%;
padding: 12px;
border: 1px solid #ddd;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.calc-btn {
background-color: #e63946;
color: white;
padding: 15px 30px;
border: none;
border-radius: 4px;
cursor: pointer;
font-size: 18px;
font-weight: bold;
width: 100%;
transition: background-color 0.3s;
}
.calc-btn:hover {
background-color: #d62839;
}
.result-box {
margin-top: 25px;
padding: 20px;
background-color: #f1faee;
border-left: 5px solid #457b9d;
border-radius: 4px;
display: none;
}
.result-title {
font-size: 18px;
color: #1d3557;
margin-bottom: 10px;
}
.result-value {
font-size: 32px;
font-weight: bold;
color: #e63946;
}
.result-detail {
font-size: 14px;
color: #666;
margin-top: 5px;
}
.seo-content h2 {
color: #1d3557;
margin-top: 30px;
}
.seo-content h3 {
color: #457b9d;
margin-top: 20px;
}
.seo-content p {
line-height: 1.6;
color: #444;
margin-bottom: 15px;
}
.seo-content ul {
margin-bottom: 20px;
padding-left: 20px;
}
.seo-content li {
margin-bottom: 8px;
line-height: 1.6;
}
.zone-table {
width: 100%;
border-collapse: collapse;
margin: 20px 0;
}
.zone-table th, .zone-table td {
border: 1px solid #ddd;
padding: 12px;
text-align: left;
}
.zone-table th {
background-color: #f1f1f1;
font-weight: 600;
}
function calculateFatBurn() {
var ageInput = document.getElementById('inputAge').value;
var rhrInput = document.getElementById('inputRHR').value;
var resultBox = document.getElementById('resultOutput');
var zoneDisplay = document.getElementById('zoneRange');
var maxHrDisplay = document.getElementById('maxHrDisplay');
var methodDisplay = document.getElementById('methodUsed');
// Validation
if (!ageInput || isNaN(ageInput) || ageInput 110) {
alert("Please enter a valid age between 10 and 110.");
return;
}
var age = parseInt(ageInput);
var maxHR = 220 – age; // Standard max heart rate formula
var rhr = parseFloat(rhrInput);
var lowZone, highZone;
var method = "";
// Check if RHR is provided for Karvonen Formula
if (!isNaN(rhr) && rhr > 30 && rhr < 150) {
// Karvonen Formula
// Target HR = ((MaxHR – RHR) * Intensity) + RHR
// Fat Burn Zone is typically 60% to 70% intensity
var hrr = maxHR – rhr; // Heart Rate Reserve
lowZone = Math.round((hrr * 0.60) + rhr);
highZone = Math.round((hrr * 0.70) + rhr);
method = "Calculation based on the Karvonen Formula (considering resting heart rate).";
} else {
// Standard Percentage Method
// Fat Burn Zone is 60% to 70% of Max HR
lowZone = Math.round(maxHR * 0.60);
highZone = Math.round(maxHR * 0.70);
method = "Calculation based on Standard Max Heart Rate percentage.";
}
// Display Results
zoneDisplay.innerHTML = lowZone + " – " + highZone + " BPM";
maxHrDisplay.innerHTML = "Estimated Maximum Heart Rate:
";
methodDisplay.innerHTML = method;
resultBox.style.display = "block";
}
How to Calculate Your Heart Rate for Fat Burn
Finding the "sweet spot" for exercise intensity is crucial if your primary goal is to burn fat. While high-intensity workouts have their place, the body primarily utilizes fat as a fuel source when operating within a specific aerobic zone. This calculator helps you identify that range so you can optimize your cardio sessions.
The Science Behind the Fat Burn Zone
Your body relies on two main fuel sources during exercise: glycogen (stored sugar) and fat. The proportion of fuel used depends largely on the intensity of the activity:
- Low to Moderate Intensity (60-70% Max HR): The body has enough oxygen available to oxidize fat for energy. This is often called the "Fat Burn Zone."
- High Intensity (70-90% Max HR): The body requires energy faster than oxygen can be processed to burn fat, so it switches to burning glycogen. While you burn more calories overall, a lower percentage comes from fat stores.
Understanding the Formulas
This calculator utilizes two primary methods depending on the data you provide:
1. The Standard Method (MHR)
This is the simplest way to estimate your zones. It first calculates your Maximum Heart Rate (MHR) using the formula 220 - Age. The fat burn zone is then calculated as 60% to 70% of that maximum.
2. The Karvonen Formula (Preferred)
If you enter your Resting Heart Rate (RHR), the calculator uses the Karvonen formula. This is generally more accurate because it takes into account your specific fitness level. The formula is:
Target HR = ((Max HR - Resting HR) × % Intensity) + Resting HR
People with better cardiovascular fitness generally have lower resting heart rates, and this formula adjusts the training zones upward to ensure they are working hard enough to see results.
Heart Rate Zone Reference Chart
| Zone |
Intensity (%) |
Benefit |
| Warm Up |
50-60% |
Improves overall health and helps recovery. |
| Fat Burn |
60-70% |
Maximal fat oxidation and basic endurance. |
| Aerobic |
70-80% |
Improves cardiovascular fitness and stamina. |
| Anaerobic |
80-90% |
Increases maximum performance capacity. |
Tips for Training in the Fat Burn Zone
- Consistency is Key: Aim for longer duration workouts (30-60 minutes) to maximize fat oxidation.
- Monitor Your Pulse: Use a wearable fitness tracker or manually check your pulse at your wrist or neck for 15 seconds and multiply by 4.
- The Talk Test: If you don't have a monitor, use the "talk test." In the fat burn zone, you should be able to carry on a conversation, though you might be breathing slightly heavier than normal.
Disclaimer: These calculations provide estimates. Please consult with a healthcare professional or a certified trainer before starting a new exercise regimen, especially if you have existing health conditions.