Heart Rate Calculator

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Heart Rate Zone Calculator

Estimated Maximum Heart Rate:
0 BPM
Zone & Intensity BPM Range Benefit
function calculateHeartZones() { var age = parseFloat(document.getElementById('userAge').value); var rhr = parseFloat(document.getElementById('restingHR').value); var resultArea = document.getElementById('hrResultArea'); var tableBody = document.getElementById('zoneTableBody'); var maxHRDisplay = document.getElementById('maxHRValue'); if (isNaN(age) || age 120) { alert("Please enter a valid age."); return; } if (isNaN(rhr) || rhr 200) { alert("Please enter a realistic resting heart rate (30-200 BPM)."); return; } // Fox Formula for MHR var mhr = 220 – age; // Heart Rate Reserve (Karvonen) var hrr = mhr – rhr; maxHRDisplay.innerText = Math.round(mhr); var zones = [ { name: "Zone 1 (50-60%)", low: 0.50, high: 0.60, benefit: "Warm-up / Recovery", color: "#e3f2fd" }, { name: "Zone 2 (60-70%)", low: 0.60, high: 0.70, benefit: "Fat Burn / Base Endurance", color: "#e8f5e9" }, { name: "Zone 3 (70-80%)", low: 0.70, high: 0.80, benefit: "Aerobic / Fitness", color: "#fffde7" }, { name: "Zone 4 (80-90%)", low: 0.80, high: 0.90, benefit: "Anaerobic / Speed", color: "#fff3e0" }, { name: "Zone 5 (90-100%)", low: 0.90, high: 1.00, benefit: "Max Effort / Power", color: "#ffebee" } ]; var html = ""; for (var i = 0; i < zones.length; i++) { var zoneLow = Math.round((hrr * zones[i].low) + rhr); var zoneHigh = Math.round((hrr * zones[i].high) + rhr); html += ''; html += '' + zones[i].name + ''; html += '' + zoneLow + ' – ' + zoneHigh + ' BPM'; html += '' + zones[i].benefit + ''; html += ''; } tableBody.innerHTML = html; resultArea.style.display = 'block'; }

Understanding Heart Rate Zones

A heart rate calculator is an essential tool for athletes, fitness enthusiasts, and anyone looking to optimize their cardiovascular health. By determining your target heart rate zones, you can tailor your workouts to achieve specific goals—whether that's burning fat, increasing aerobic capacity, or improving sprint speed.

How Calculation Works

This tool utilizes the Karvonen Formula, which is widely considered more accurate than simple percentage-of-max-heart-rate calculations. This formula factors in your Resting Heart Rate (RHR) to determine your Heart Rate Reserve (HRR). The HRR represents the range of beats available for exercise above your resting state.

The Math:
1. Max Heart Rate (MHR) = 220 – Age
2. Heart Rate Reserve (HRR) = MHR – Resting HR
3. Target HR = (HRR × Intensity%) + Resting HR

Training Zone Breakdown

  • Zone 1 (Very Light): Ideal for active recovery and warming up. Improves overall health and helps with recovery after harder sessions.
  • Zone 2 (Light): Often called the "Fat Burning Zone." It builds basic endurance and prepares the body for higher-intensity training by improving mitochondrial efficiency.
  • Zone 3 (Moderate): The aerobic zone. Training here improves your cardiovascular system and lung capacity. You can usually maintain this for a long duration.
  • Zone 4 (Hard): The anaerobic zone. You begin to produce lactic acid faster than your body can clear it. This increases your speed and high-intensity endurance.
  • Zone 5 (Maximum): Red-line effort. Only sustainable for very short bursts (seconds to a couple of minutes). This develops peak power and neurological speed.

Practical Example

Imagine a 40-year-old individual with a resting heart rate of 70 BPM. Their calculated Max HR would be 180 (220 – 40). Their Heart Rate Reserve is 110 (180 – 70). To train in the Aerobic Zone (75%), the calculation would be: (110 * 0.75) + 70 = 152 BPM.

Disclaimer: This calculator is for informational purposes only. Always consult with a physician before starting a new exercise regimen, especially if you have pre-existing cardiovascular conditions or are taking medications that affect heart rate.

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