/* Calculator specific styles to ensure isolation in WordPress */
.fat-burn-calculator-container {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 20px auto;
background: #ffffff;
border: 1px solid #e0e0e0;
border-radius: 8px;
box-shadow: 0 4px 12px rgba(0,0,0,0.05);
overflow: hidden;
}
.fbc-header {
background: #e74c3c;
color: white;
padding: 20px;
text-align: center;
}
.fbc-header h2 {
margin: 0;
font-size: 24px;
color: white;
}
.fbc-body {
padding: 25px;
display: flex;
flex-wrap: wrap;
gap: 20px;
}
.fbc-input-group {
flex: 1 1 300px;
display: flex;
flex-direction: column;
}
.fbc-input-group label {
font-weight: 600;
margin-bottom: 8px;
color: #333;
font-size: 14px;
}
.fbc-input-group input {
padding: 12px;
border: 1px solid #ddd;
border-radius: 4px;
font-size: 16px;
transition: border 0.3s;
}
.fbc-input-group input:focus {
border-color: #e74c3c;
outline: none;
}
.fbc-input-note {
font-size: 12px;
color: #777;
margin-top: 5px;
}
.fbc-controls {
width: 100%;
text-align: center;
margin-top: 10px;
}
.fbc-btn {
background: #e74c3c;
color: white;
border: none;
padding: 15px 40px;
font-size: 18px;
font-weight: bold;
border-radius: 5px;
cursor: pointer;
transition: background 0.2s;
width: 100%;
max-width: 300px;
}
.fbc-btn:hover {
background: #c0392b;
}
.fbc-result-container {
background: #f9f9f9;
padding: 25px;
border-top: 1px solid #eee;
display: none; /* Hidden by default */
}
.fbc-result-box {
text-align: center;
margin-bottom: 20px;
}
.fbc-result-value {
font-size: 36px;
font-weight: 800;
color: #e74c3c;
margin: 10px 0;
}
.fbc-result-label {
font-size: 16px;
color: #555;
text-transform: uppercase;
letter-spacing: 1px;
}
.fbc-details {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 15px;
margin-top: 20px;
}
.fbc-detail-item {
background: white;
padding: 15px;
border-radius: 6px;
border: 1px solid #eee;
text-align: center;
}
.fbc-detail-title {
font-size: 13px;
color: #888;
margin-bottom: 5px;
}
.fbc-detail-num {
font-size: 20px;
font-weight: 700;
color: #333;
}
.seo-content {
max-width: 800px;
margin: 40px auto;
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
line-height: 1.6;
color: #333;
}
.seo-content h2 {
color: #2c3e50;
margin-top: 30px;
border-bottom: 2px solid #e74c3c;
padding-bottom: 10px;
display: inline-block;
}
.seo-content h3 {
color: #34495e;
margin-top: 25px;
}
.seo-content p {
margin-bottom: 15px;
}
.seo-content ul {
margin-bottom: 15px;
padding-left: 20px;
}
.seo-content li {
margin-bottom: 8px;
}
@media (max-width: 600px) {
.fbc-body {
flex-direction: column;
}
.fbc-details {
grid-template-columns: 1fr;
}
}
function calculateFatBurn() {
// 1. Get input values
var ageInput = document.getElementById("fb_age");
var rhrInput = document.getElementById("fb_rhr");
var age = parseFloat(ageInput.value);
var rhr = parseFloat(rhrInput.value);
// 2. Validation
if (isNaN(age) || age 120) {
alert("Please enter a valid age between 10 and 120.");
return;
}
if (isNaN(rhr) || rhr 200) {
alert("Please enter a valid resting heart rate (typically 40-100 bpm).");
return;
}
// 3. Calculation Logic (Karvonen Method)
// Standard Max Heart Rate Formula
var maxHeartRate = 220 – age;
// Heart Rate Reserve (HRR) = Max – Resting
var heartRateReserve = maxHeartRate – rhr;
// Fat Burning Zone is typically 60% to 70% intensity using Karvonen
// Formula: (HRR * Intensity%) + RHR
var minIntensity = 0.60;
var maxIntensity = 0.70;
var lowerZoneLimit = Math.round((heartRateReserve * minIntensity) + rhr);
var upperZoneLimit = Math.round((heartRateReserve * maxIntensity) + rhr);
// 4. Update the DOM
document.getElementById("fb_display_mhr").innerHTML = maxHeartRate + " BPM";
document.getElementById("fb_display_hrr").innerHTML = heartRateReserve + " BPM";
document.getElementById("fb_display_min").innerHTML = lowerZoneLimit + " BPM";
document.getElementById("fb_display_max").innerHTML = upperZoneLimit + " BPM";
document.getElementById("fb_display_zone").innerHTML = lowerZoneLimit + " – " + upperZoneLimit + " BPM";
// Show result div
document.getElementById("fb_result_area").style.display = "block";
}
How to Calculate Best Heart Rate for Fat Burning
Finding your optimal heart rate for fat burning is one of the most effective ways to improve body composition and metabolic health. Unlike high-intensity intervals that burn glycogen (carbohydrates), the "fat burning zone" utilizes aerobic lipolysis—a process where your body primarily uses stored fat for fuel.
This calculator uses the Karvonen Formula, widely considered the gold standard for determining personal heart rate zones because it accounts for your resting heart rate, offering a much more personalized target than generic charts.
Understanding the Fat Burning Zone
The "fat burning zone" is typically defined as a low-to-moderate intensity exercise level, usually between 60% and 70% of your Heart Rate Reserve (HRR). In this zone:
- Oxygen is readily available to cells.
- Fat oxidation is maximized because fat requires oxygen to break down.
- Lactic acid accumulation is minimal, allowing for longer duration workouts.
The Mathematics Behind the Calculator
While the standard formula for Maximum Heart Rate (MHR) is simply 220 minus your age, this is only the first step. To find your true fat-burning potential, we must consider your fitness level via your Resting Heart Rate (RHR).
Step 1: Calculate Maximum Heart Rate (MHR)
MHR = 220 - Age
For example, a 40-year-old would have an estimated MHR of 180 beats per minute (BPM).
Step 2: Calculate Heart Rate Reserve (HRR)
HRR = MHR - Resting Heart Rate
If that 40-year-old has a resting heart rate of 60 BPM, their HRR is 120 (180 – 60).
Step 3: Calculate the Target Zone
We apply the intensity percentage to the Reserve, then add the Resting Heart Rate back in:
Target = (HRR × Intensity%) + RHR
Using 60% intensity: (120 × 0.60) + 60 = 132 BPM.
Why Resting Heart Rate Matters
Two people of the same age can have vastly different cardiovascular capabilities. An athlete with a low resting heart rate has a larger "reserve" effectively allowing them to work harder while still remaining in an aerobic state. By inputting your specific resting heart rate, this tool adjusts the intensity zones to match your actual cardiovascular fitness.
How to Use These Numbers
Once you have calculated your range (e.g., 132–144 BPM), aim to keep your heart rate within this window for steady-state cardio sessions lasting 30 to 60 minutes. Activities that commonly fall into this category include brisk walking, light jogging, cycling on flat terrain, or using an elliptical machine at a moderate pace.