.calculator-wrapper {
max-width: 800px;
margin: 0 auto;
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
background: #fff;
padding: 20px;
border-radius: 8px;
box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}
.calc-header {
text-align: center;
margin-bottom: 25px;
background: #f8f9fa;
padding: 15px;
border-radius: 8px;
border-left: 5px solid #28a745;
}
.calc-header h3 {
margin: 0;
color: #2c3e50;
font-size: 24px;
}
.input-group {
margin-bottom: 20px;
}
.input-group label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #333;
}
.input-group input {
width: 100%;
padding: 12px;
border: 1px solid #ddd;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.input-group input:focus {
border-color: #28a745;
outline: none;
box-shadow: 0 0 0 2px rgba(40, 167, 69, 0.2);
}
.help-text {
font-size: 12px;
color: #666;
margin-top: 5px;
}
.calc-btn {
width: 100%;
padding: 15px;
background: #28a745;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
font-weight: bold;
cursor: pointer;
transition: background 0.3s;
}
.calc-btn:hover {
background: #218838;
}
#results-area {
margin-top: 30px;
display: none;
background: #fdfdfd;
border: 1px solid #e9ecef;
border-radius: 8px;
padding: 20px;
}
.result-box {
text-align: center;
margin-bottom: 20px;
padding-bottom: 20px;
border-bottom: 1px solid #eee;
}
.result-box:last-child {
border-bottom: none;
margin-bottom: 0;
padding-bottom: 0;
}
.result-label {
font-size: 14px;
text-transform: uppercase;
letter-spacing: 1px;
color: #666;
margin-bottom: 10px;
}
.result-value {
font-size: 36px;
font-weight: 800;
color: #28a745;
}
.result-sub {
font-size: 14px;
color: #555;
margin-top: 5px;
}
.zone-visual {
height: 20px;
background: #e9ecef;
border-radius: 10px;
margin-top: 15px;
overflow: hidden;
position: relative;
}
.zone-bar {
height: 100%;
background: linear-gradient(90deg, #ffc107, #28a745, #ffc107);
width: 50%;
margin-left: 25%;
}
/* Content Styling */
.content-section {
margin-top: 40px;
line-height: 1.6;
color: #333;
}
.content-section h2 {
color: #2c3e50;
margin-top: 30px;
border-bottom: 2px solid #28a745;
padding-bottom: 10px;
display: inline-block;
}
.content-section h3 {
color: #333;
margin-top: 25px;
}
.content-section ul {
background: #f8f9fa;
padding: 20px 40px;
border-radius: 8px;
}
.content-section p {
margin-bottom: 15px;
}
.info-box {
background-color: #e8f5e9;
border-left: 4px solid #28a745;
padding: 15px;
margin: 20px 0;
}
@media (max-width: 600px) {
.result-value {
font-size: 28px;
}
}
function calculateHeartRate() {
// Get inputs
var ageInput = document.getElementById('ageInput');
var rhrInput = document.getElementById('rhrInput');
var age = parseInt(ageInput.value);
var rhr = parseInt(rhrInput.value);
// Validation
if (!age || age 120) {
alert("Please enter a valid age between 1 and 120.");
return;
}
// Calculate Maximum Heart Rate (Standard Formula)
var mhr = 220 – age;
var lowerZone = 0;
var upperZone = 0;
var methodUsed = "";
// Logic: Check if Resting Heart Rate is provided and valid
if (!isNaN(rhr) && rhr > 20 && rhr < 200) {
// KARVONEN FORMULA (Heart Rate Reserve Method)
// HRR = MHR – RHR
// Target = (HRR * %) + RHR
var hrr = mhr – rhr;
// 60% intensity
lowerZone = Math.round((hrr * 0.60) + rhr);
// 70% intensity
upperZone = Math.round((hrr * 0.70) + rhr);
methodUsed = "Karvonen Formula (Accounting for Resting Heart Rate)";
} else {
// STANDARD FORMULA (Percentage of MHR)
// Target = MHR * %
lowerZone = Math.round(mhr * 0.60);
upperZone = Math.round(mhr * 0.70);
methodUsed = "Standard Formula (Percentage of Max Heart Rate)";
}
// Display Results
document.getElementById('zoneResult').innerHTML = lowerZone + " – " + upperZone + " bpm";
document.getElementById('mhrResult').innerHTML = mhr + " bpm";
document.getElementById('methodText').innerText = methodUsed;
// Show results area
document.getElementById('results-area').style.display = 'block';
// Scroll to results
document.getElementById('results-area').scrollIntoView({ behavior: 'smooth' });
}
Target Heart Rate Calculator: Fat Burning Zone
Your maximum heart rate is primarily determined by age.
Leave blank for the standard formula, or enter for the more accurate Karvonen method.
Optimal Fat Burning Zone (60% – 70%)
111 – 129 bpm
Beats Per Minute
Maximum Heart Rate (MHR)
185 bpm
Estimated Theoretical Max
Calculation Method: Standard Formula (220 – Age)
What is the Fat Burning Zone?
The "fat burning zone" refers to a specific intensity of physical activity where your body primarily relies on stored fat as its fuel source. Physiologically, this typically occurs when your heart rate is between 60% and 70% of your maximum heart rate (MHR).
While high-intensity exercise burns more calories overall, lower-intensity exercise in this specific zone metabolizes a higher percentage of calories from fat. This makes it a popular target for individuals specifically looking to manage weight through steady-state cardio, such as walking, jogging, or cycling.
Key Benefit: Training in this zone is sustainable for longer durations, allowing for extended calorie expenditure without the rapid fatigue associated with high-intensity interval training (HIIT).
How This Calculator Works
This tool utilizes two primary methods to determine your target heart rate, depending on the data you provide:
1. The Standard Formula (MHR Method)
If you only enter your age, we use the standard Maximum Heart Rate formula:
- MHR = 220 – Age
- Lower Limit = MHR × 0.60
- Upper Limit = MHR × 0.70
2. The Karvonen Formula (HRR Method)
If you enter your Resting Heart Rate (RHR), the calculator automatically switches to the more accurate Karvonen formula. This method accounts for your specific fitness level by calculating your Heart Rate Reserve (HRR).
- HRR = MHR – Resting Heart Rate
- Target HR = (HRR × Intensity%) + Resting Heart Rate
The Karvonen method is generally preferred for individuals who are very fit (low resting heart rate) or older, as it prevents the target zones from being set too low.
Tips for Reaching Your Zone
To effectively train in the fat burning zone:
- Monitor Your Pulse: Use a smartwatch, heart rate monitor, or manually take your pulse at your wrist or neck for 15 seconds and multiply by 4.
- The "Talk Test": You should be able to carry on a conversation while exercising. If you are gasping for air, you are likely in a higher aerobic or anaerobic zone.
- Consistency is Key: Aim for 30 to 60 minutes of activity in this zone, 3 to 5 times per week.