.hr-calc-input-group { margin-bottom: 20px; }
.hr-calc-input-group label { display: block; font-weight: 600; margin-bottom: 8px; color: #2c3e50; }
.hr-calc-input-group input { width: 100%; padding: 12px; border: 2px solid #ddd; border-radius: 6px; box-sizing: border-box; font-size: 16px; transition: border-color 0.3s; }
.hr-calc-input-group input:focus { border-color: #e74c3c; outline: none; }
.hr-calc-btn { background-color: #e74c3c; color: white; padding: 14px 24px; border: none; border-radius: 6px; cursor: pointer; font-size: 18px; font-weight: bold; width: 100%; transition: background-color 0.3s; }
.hr-calc-btn:hover { background-color: #c0392b; }
#hr-calc-result { margin-top: 25px; display: none; }
.zone-card { padding: 15px; border-left: 5px solid #ccc; margin-bottom: 10px; background: #f9f9f9; border-radius: 0 6px 6px 0; }
.zone-1 { border-left-color: #3498db; }
.zone-2 { border-left-color: #2ecc71; }
.zone-3 { border-left-color: #f1c40f; }
.zone-4 { border-left-color: #e67e22; }
.zone-5 { border-left-color: #e74c3c; }
.zone-title { font-weight: bold; font-size: 1.1em; }
.zone-desc { font-size: 0.9em; color: #666; }
.mhr-display { text-align: center; margin-bottom: 20px; padding: 15px; background: #fdf2f2; border-radius: 8px; border: 1px solid #fadbd8; }
.mhr-value { font-size: 24px; font-weight: bold; color: #e74c3c; }
function calculateHeartZones() {
var ageInput = document.getElementById('hrAge').value;
var rhrInput = document.getElementById('hrResting').value;
var age = parseInt(ageInput);
var rhr = parseInt(rhrInput) || 0; // Default to 0 if not provided
if (!age || age 120) {
alert("Please enter a valid age.");
return;
}
// Estimate MHR using Fox Formula
var mhr = 220 – age;
var reserve = mhr – rhr;
document.getElementById('valMHR').innerHTML = mhr;
function getRange(minPercent, maxPercent) {
var min, max;
if (rhr > 0) {
// Karvonen Formula
min = Math.round((reserve * minPercent) + rhr);
max = Math.round((reserve * maxPercent) + rhr);
} else {
// Simple Percentage
min = Math.round(mhr * minPercent);
max = Math.round(mhr * maxPercent);
}
return min + " – " + max + " BPM";
}
document.getElementById('z1Range').innerText = getRange(0.50, 0.60);
document.getElementById('z2Range').innerText = getRange(0.60, 0.70);
document.getElementById('z3Range').innerText = getRange(0.70, 0.80);
document.getElementById('z4Range').innerText = getRange(0.80, 0.90);
document.getElementById('z5Range').innerText = getRange(0.90, 1.00);
document.getElementById('hr-calc-result').style.display = 'block';
// Scroll to results on mobile
document.getElementById('hr-calc-result').scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}
Heart Rate Burn Zone Calculator
Optimize your workouts by identifying your ideal heart rate intensities for fat loss and endurance.
Estimated Max Heart Rate (MHR): 0 BPM
Zone 1: Warm Up (50-60%)
0 – 0 BPM
Best for: Recovery, metabolism stimulation, and beginners.
Zone 2: Fat Burning (60-70%)
0 – 0 BPM
Best for: Efficient fat loss, aerobic base building, and long sessions.
Zone 3: Aerobic / Cardio (70-80%)
0 – 0 BPM
Best for: Improving cardiovascular endurance and lung capacity.
Zone 4: Anaerobic / Threshold (80-90%)
0 – 0 BPM
Best for: High-speed endurance and improving performance limit.
Zone 5: Peak / Red Line (90-100%)
0 – 0 BPM
Best for: Maximum performance and short interval sprints.
How Target Heart Rate Zones Work
Training with a heart rate monitor allows you to gauge the intensity of your exercise accurately. Instead of guessing how hard you are working, heart rate zones provide objective data based on your physiology.
Understanding the Zones
- Fat Burning Zone (60-70%): In this zone, the body uses a higher percentage of fat for fuel versus carbohydrates. While you burn fewer total calories than at high intensities, the caloric expenditure is sustainably fat-focused.
- Cardio Zone (70-80%): This is the sweet spot for improving heart health and stamina. It strengthens your heart and increases the size and number of blood vessels in your muscles.
- Anaerobic Zone (80-90%): Training here improves your VO2 max and your ability to tolerate lactic acid. This is typical for HIIT (High-Intensity Interval Training).
The Karvonen Formula vs. Standard Formula
This calculator uses a hybrid approach. If you provide your Resting Heart Rate (RHR), it applies the Karvonen Formula, which takes your "Heart Rate Reserve" into account. This is generally more accurate for fit individuals as it tailors the percentages to your specific cardiovascular baseline.
Example Calculation
If a 40-year-old individual has a resting heart rate of 70 BPM:
- Max Heart Rate (MHR) = 220 – 40 = 180 BPM.
- Heart Rate Reserve (HRR) = 180 – 70 = 110 BPM.
- 60% Fat Burn Low End = (110 * 0.60) + 70 = 136 BPM.
- 70% Fat Burn High End = (110 * 0.70) + 70 = 147 BPM.
This individual's ideal fat-burning zone would be between 136 and 147 beats per minute.