.fbhrc-container {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 0 auto;
padding: 20px;
background: #ffffff;
color: #333;
}
.fbhrc-calculator-card {
background: #f8f9fa;
border: 1px solid #e9ecef;
border-radius: 8px;
padding: 30px;
margin-bottom: 40px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.fbhrc-title {
text-align: center;
color: #2c3e50;
margin-bottom: 25px;
font-size: 24px;
font-weight: 700;
}
.fbhrc-input-group {
margin-bottom: 20px;
}
.fbhrc-label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #495057;
}
.fbhrc-input {
width: 100%;
padding: 12px;
border: 2px solid #ced4da;
border-radius: 6px;
font-size: 16px;
box-sizing: border-box;
transition: border-color 0.3s;
}
.fbhrc-input:focus {
border-color: #e74c3c;
outline: none;
}
.fbhrc-btn {
display: block;
width: 100%;
padding: 15px;
background: #e74c3c;
color: white;
border: none;
border-radius: 6px;
font-size: 18px;
font-weight: bold;
cursor: pointer;
transition: background 0.3s;
margin-top: 20px;
}
.fbhrc-btn:hover {
background: #c0392b;
}
.fbhrc-result-box {
margin-top: 30px;
padding: 20px;
background: #fff;
border-left: 5px solid #e74c3c;
border-radius: 4px;
display: none;
box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}
.fbhrc-result-title {
font-size: 20px;
color: #2c3e50;
margin-bottom: 15px;
font-weight: 700;
}
.fbhrc-stat-row {
display: flex;
justify-content: space-between;
padding: 10px 0;
border-bottom: 1px solid #eee;
}
.fbhrc-stat-row:last-child {
border-bottom: none;
}
.fbhrc-stat-label {
font-weight: 500;
}
.fbhrc-stat-value {
font-weight: 700;
color: #e74c3c;
}
.fbhrc-article h2 {
color: #2c3e50;
margin-top: 35px;
font-size: 22px;
border-bottom: 2px solid #e74c3c;
padding-bottom: 10px;
display: inline-block;
}
.fbhrc-article p {
line-height: 1.6;
margin-bottom: 15px;
color: #555;
}
.fbhrc-article ul {
margin-bottom: 20px;
padding-left: 20px;
}
.fbhrc-article li {
margin-bottom: 10px;
line-height: 1.6;
}
.fbhrc-small-text {
font-size: 12px;
color: #7f8c8d;
margin-top: 5px;
}
function calculateFatBurn() {
// Get inputs
var ageInput = document.getElementById('userAge');
var rhrInput = document.getElementById('restingHR');
var resultBox = document.getElementById('resultOutput');
var age = parseFloat(ageInput.value);
var rhr = parseFloat(rhrInput.value);
// Validation
if (isNaN(age) || age 120) {
alert("Please enter a valid age.");
return;
}
// Calculate Maximum Heart Rate (Standard Formula)
var mhr = 220 – age;
var fatBurnMin, fatBurnMax, cardioMin, cardioMax, anaerobicMin, anaerobicMax;
var isKarvonen = false;
// Check if RHR is provided and valid for Karvonen formula
if (!isNaN(rhr) && rhr > 30 && rhr < 120) {
isKarvonen = true;
// Karvonen Formula: Target = ((MHR – RHR) * %) + RHR
var hrr = mhr – rhr; // Heart Rate Reserve
fatBurnMin = Math.round((hrr * 0.60) + rhr);
fatBurnMax = Math.round((hrr * 0.70) + rhr);
cardioMin = Math.round((hrr * 0.70) + rhr);
cardioMax = Math.round((hrr * 0.80) + rhr);
anaerobicMin = Math.round((hrr * 0.80) + rhr);
anaerobicMax = Math.round((hrr * 0.90) + rhr);
} else {
// Standard Percentage Method
fatBurnMin = Math.round(mhr * 0.60);
fatBurnMax = Math.round(mhr * 0.70);
cardioMin = Math.round(mhr * 0.70);
cardioMax = Math.round(mhr * 0.80);
anaerobicMin = Math.round(mhr * 0.80);
anaerobicMax = Math.round(mhr * 0.90);
}
// Display Results
document.getElementById('resMHR').innerHTML = mhr + " bpm";
document.getElementById('resFatBurn').innerHTML = fatBurnMin + " – " + fatBurnMax + " bpm";
document.getElementById('resCardio').innerHTML = cardioMin + " – " + cardioMax + " bpm";
document.getElementById('resAnaerobic').innerHTML = anaerobicMin + " – " + anaerobicMax + " bpm";
// Show result box
resultBox.style.display = "block";
// Scroll to results slightly
resultBox.scrollIntoView({behavior: "smooth", block: "nearest"});
}
Fat Burning Heart Rate Calculator
Leave blank if unknown. Providing this uses the more accurate Karvonen Formula.
Your Results
Maximum Heart Rate (MHR):
–
🔥 Fat Burning Zone (60-70%):
–
Aerobic / Cardio Zone (70-80%):
–
Anaerobic Zone (80-90%):
–
What Heart Rate Burns Fat?
When aiming for weight loss, understanding "what heart rate burns fat" is essential for maximizing the efficiency of your workouts. The human body utilizes different energy sources—primarily fats and carbohydrates (glycogen)—depending on the intensity of physical activity.
The Fat Burning Zone typically occurs at a lower intensity, specifically between 60% and 70% of your Maximum Heart Rate (MHR). In this zone, your body relies mainly on stored fat as fuel because fat requires oxygen to be broken down, and at lower intensities, your oxygen intake is sufficient to support this process.
How the Calculation Works
This calculator uses two primary methods to determine your optimal training zones:
- Standard Method (MHR): This estimates your Maximum Heart Rate using the formula 220 – Age. The zones are then calculated as simple percentages of this number.
- Karvonen Formula: If you input your Resting Heart Rate (RHR), the calculator uses the Karvonen method. This is considered more accurate because it accounts for your individual fitness level. The formula is:
Target HR = ((Max HR − Resting HR) × %Intensity) + Resting HR.
Understanding Your Heart Rate Zones
It is important to mix your training intensities for overall health, but knowing your zones helps target specific goals:
- Fat Burning Zone (60-70%): Ideal for longer duration, low-impact exercise like brisk walking or slow jogging. While the percentage of calories burned from fat is highest here, the total calorie burn is lower per minute.
- Aerobic / Cardio Zone (70-80%): This improves cardiovascular fitness. You burn a mix of fat and carbohydrates. You burn more total calories here than in the fat-burning zone, which can lead to greater overall weight loss even if the percentage from fat is lower.
- Anaerobic Zone (80-90%): High-intensity interval training (HIIT). This burns glycogen rapidly and creates an "afterburn" effect, boosting metabolism for hours after the workout.
How to Measure Your Resting Heart Rate
To get the most accurate result from the "what heart rate burns fat calculator," measure your resting heart rate right after you wake up in the morning, before getting out of bed. Count your pulse for 60 seconds. A lower resting heart rate generally indicates better cardiovascular fitness.