.calculator-container {
max-width: 800px;
margin: 0 auto;
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
color: #333;
line-height: 1.6;
}
.calc-box {
background: #f9fbfd;
border: 1px solid #e1e4e8;
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: #d63384;
margin-bottom: 25px;
font-size: 24px;
font-weight: 700;
}
.input-group {
margin-bottom: 20px;
}
.input-group label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #4a5568;
}
.input-group input, .input-group select {
width: 100%;
padding: 12px;
border: 1px solid #cbd5e0;
border-radius: 6px;
font-size: 16px;
box-sizing: border-box;
transition: border-color 0.2s;
}
.input-group input:focus, .input-group select:focus {
border-color: #d63384;
outline: none;
}
.calc-btn {
display: block;
width: 100%;
background: #d63384;
color: white;
border: none;
padding: 15px;
font-size: 18px;
font-weight: bold;
border-radius: 6px;
cursor: pointer;
transition: background 0.2s;
}
.calc-btn:hover {
background: #b8256e;
}
.result-box {
margin-top: 25px;
padding: 20px;
background: #fff;
border-left: 5px solid #d63384;
border-radius: 4px;
display: none;
animation: fadeIn 0.5s;
}
@keyframes fadeIn {
from { opacity: 0; transform: translateY(10px); }
to { opacity: 1; transform: translateY(0); }
}
.result-value {
font-size: 32px;
font-weight: 800;
color: #2d3748;
margin: 10px 0;
}
.result-label {
font-size: 14px;
color: #718096;
text-transform: uppercase;
letter-spacing: 1px;
}
.result-context {
margin-top: 15px;
font-size: 15px;
color: #4a5568;
background: #fff5f9;
padding: 10px;
border-radius: 4px;
}
.article-content h2 {
color: #2d3748;
margin-top: 35px;
border-bottom: 2px solid #edf2f7;
padding-bottom: 10px;
}
.article-content p {
margin-bottom: 15px;
}
.article-content ul {
margin-bottom: 20px;
padding-left: 20px;
}
.article-content li {
margin-bottom: 8px;
}
.info-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
margin: 20px 0;
}
@media (max-width: 600px) {
.info-grid { grid-template-columns: 1fr; }
}
.info-card {
background: #f7fafc;
padding: 15px;
border-radius: 6px;
}
.error-msg {
color: #e53e3e;
font-size: 14px;
margin-top: 5px;
display: none;
}
What Does 70% of Maximum Heart Rate Mean?
Calculating 70% of your maximum heart rate (MHR) places you squarely in the moderate intensity aerobic zone. This specific intensity level is widely regarded by physiologists and fitness experts as the "sweet spot" for improving cardiovascular endurance and burning fat effectively without overtraining.
When you exercise at 70% of your MHR, your body relies primarily on aerobic metabolism. This means your cardiovascular system works to supply oxygen to your muscles efficiently. Training at this level allows you to sustain activity for longer durations, which is crucial for heart health and building a solid fitness base.
Why Target the 70% Zone?
The 70% threshold is often referred to as the start of the "steady state" or "Zone 2/3" training. Here are the primary benefits of training at this intensity:
- Fat Utilization: At roughly 70% MHR, the body is highly efficient at oxidizing fat for fuel rather than depleting glycogen stores rapidly.
- Capillary Density: Sustained training at this level increases the number of small blood vessels in your muscles, improving oxygen delivery.
- Mitochondrial Efficiency: It boosts the size and number of mitochondria (the powerhouses of your cells), enhancing overall energy production.
- Sustainability: Unlike high-intensity interval training (HIIT), you can train at 70% frequency without requiring prolonged recovery times.
Understanding the Calculation Formulas
This calculator offers three different methods to estimate your Maximum Heart Rate (MHR) before calculating the 70% target. While the most accurate method is a clinical stress test, these formulas provide reliable estimates for the general population:
1. Fox Formula
Formula: 220 – Age
This is the traditional standard used in most gyms and simple trackers. It is easy to calculate but tends to overestimate MHR for younger people and underestimate it for older adults.
2. Tanaka Formula
Formula: 208 – (0.7 × Age)
Published in 2001, this formula is considered more accurate for healthy adults of varying ages. It smooths out the discrepancies found in the Fox formula.
3. Gulati Formula (For Women)
Formula: 206 – (0.88 × Age)
Research suggests that women often have a slightly different heart rate decline with age compared to men. This formula is specifically calibrated for female physiology.
How to Use This Number
Once you have your calculated 70% figure (e.g., 135 BPM), use it to guide your workouts. During a run, cycle, or brisk walk, check your pulse or use a wearable heart rate monitor.
If your heart rate drifts significantly above this number (e.g., reaching 85-90%), you are entering the anaerobic zone, where lactic acid builds up, and fatigue sets in faster. If it drops significantly below (e.g., 50-60%), you may simply be in a warm-up or recovery zone. Staying near the 70% mark ensures you are getting a quality aerobic workout.
function calculateTargetHR() {
// Get inputs
var ageInput = document.getElementById('hrAge');
var methodInput = document.getElementById('calcMethod');
var resultBox = document.getElementById('hrResult');
var errorMsg = document.getElementById('ageError');
var age = parseFloat(ageInput.value);
var method = methodInput.value;
// Validation
if (isNaN(age) || age 120) {
errorMsg.style.display = 'block';
resultBox.style.display = 'none';
return;
} else {
errorMsg.style.display = 'none';
}
// MHR Calculation Logic
var mhr = 0;
if (method === 'fox') {
mhr = 220 – age;
} else if (method === 'tanaka') {
mhr = 208 – (0.7 * age);
} else if (method === 'gulati') {
mhr = 206 – (0.88 * age);
}
// Calculate 70% and Range
var target70 = Math.round(mhr * 0.70);
var mhrRounded = Math.round(mhr);
// Zone Range (65% to 75%)
var zoneLow = Math.round(mhr * 0.65);
var zoneHigh = Math.round(mhr * 0.75);
// Update UI
document.getElementById('targetValue').innerHTML = target70 + '
';
document.getElementById('maxValue').innerHTML = mhrRounded + ' BPM';
document.getElementById('zoneRange').innerHTML = zoneLow + ' – ' + zoneHigh + ' BPM';
// Dynamic Context Text
var contextDiv = document.getElementById('contextText');
contextDiv.innerHTML = '
At ' + age + ' years old using the ' +
(method === 'fox' ? 'standard Fox' : (method === 'tanaka' ? 'Tanaka' : 'Gulati')) +
' formula, your estimated maximum heart rate is
. ' +
'To train at 70% intensity, aim to keep your pulse near
. ' +
'This level allows you to hold a conversation while exercising, often called "conversational pace."';
// Show result
resultBox.style.display = 'block';
}