Cardiac Frequency Calculator

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Calculate your Maximum Heart Rate and Target Training Zones using the Karvonen Formula.

Understanding Cardiac Frequency and Your Training

Cardiac frequency, commonly known as heart rate, refers to the number of times your heart beats per minute (BPM). Monitoring your cardiac frequency is one of the most effective ways to gauge exercise intensity and ensure you are training safely and effectively within your biological limits.

The Science of Heart Rate Zones

Not all exercise is created equal. Depending on how fast your heart is beating, your body utilizes different energy systems. By using a cardiac frequency calculator, you can pinpoint exactly which "zone" you are in:

• Zone 1 (Recovery): 50-60% intensity. Best for warm-ups and active recovery after a hard workout.
• Zone 2 (Fat Burn/Aerobic Base): 60-70% intensity. This is the "sweet spot" for long-duration cardio and building endurance.
• Zone 3 (Aerobic/Endurance): 70-80% intensity. Improves cardiovascular capacity and strengthens the heart muscle.
• Zone 4 (Anaerobic/Threshold): 80-90% intensity. Increases your lactate threshold and speed.
• Zone 5 (Red Line): 90-100% intensity. Maximum effort for short bursts; improves peak performance.

How This Calculator Works

This tool uses the Karvonen Formula, which is considered more accurate than simple percentage models because it incorporates your Resting Heart Rate (RHR). The calculation determines your Heart Rate Reserve (HRR) by subtracting your resting rate from your maximum heart rate (220 – age). It then applies the target percentages to that reserve and adds back your resting rate.

Example Calculation:
If you are 30 years old with a resting heart rate of 60 BPM:
1. Max HR: 220 – 30 = 190 BPM
2. Heart Rate Reserve: 190 – 60 = 130 BPM
3. 70% Intensity: (130 * 0.70) + 60 = 151 BPM

Why Monitor Your Resting Heart Rate?

A lower resting heart rate generally indicates better cardiovascular fitness and a more efficient heart. If you notice your resting heart rate climbing significantly over several days, it may be a sign of overtraining, high stress, or an oncoming illness.

Note: Always consult with a medical professional before starting a new high-intensity exercise program, especially if you have pre-existing cardiovascular conditions.

function calculateCardiacFrequency() { var age = document.getElementById('age').value; var rhr = document.getElementById('restingHR').value; var resultsBox = document.getElementById('hr-results'); var zoneBody = document.getElementById('zone-body'); var mhrDisplay = document.getElementById('mhr-display'); var hrrDisplay = document.getElementById('hrr-display'); if (!age || age 120) { alert('Please enter a valid age.'); return; } if (!rhr || rhr <= 0) { alert('Please enter a valid resting heart rate.'); return; } var ageNum = parseFloat(age); var rhrNum = parseFloat(rhr); // Calculation var mhr = 220 – ageNum; var hrr = mhr – rhrNum; mhrDisplay.innerHTML = Math.round(mhr); hrrDisplay.innerHTML = Math.round(hrr); var zones = [ { name: "Zone 1 (Recovery)", min: 0.50, max: 0.60 }, { name: "Zone 2 (Fat Burn)", min: 0.60, max: 0.70 }, { name: "Zone 3 (Aerobic)", min: 0.70, max: 0.80 }, { name: "Zone 4 (Anaerobic)", min: 0.80, max: 0.90 }, { name: "Zone 5 (Red Line)", min: 0.90, max: 1.00 } ]; var html = ""; for (var i = 0; i < zones.length; i++) { var low = Math.round((hrr * zones[i].min) + rhrNum); var high = Math.round((hrr * zones[i].max) + rhrNum); html += ""; html += "" + zones[i].name + ""; html += "" + (zones[i].min * 100) + "% – " + (zones[i].max * 100) + "%"; html += "" + low + " – " + high + " BPM"; html += ""; } zoneBody.innerHTML = html; resultsBox.style.display = 'block'; // Scroll to results smoothly resultsBox.scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }