.calculator-container-wrapper {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 0 auto;
color: #333;
line-height: 1.6;
}
.calc-box {
background: #f8f9fa;
border: 1px solid #e9ecef;
border-radius: 8px;
padding: 30px;
margin-bottom: 40px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.calc-title {
text-align: center;
color: #2c3e50;
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: #495057;
}
.input-group input {
width: 100%;
padding: 12px;
border: 1px solid #ced4da;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.input-group .help-text {
font-size: 12px;
color: #6c757d;
margin-top: 5px;
}
.calc-btn {
width: 100%;
background-color: #e74c3c;
color: white;
border: none;
padding: 15px;
font-size: 18px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
transition: background-color 0.2s;
}
.calc-btn:hover {
background-color: #c0392b;
}
.results-box {
margin-top: 30px;
display: none;
background: #fff;
padding: 20px;
border-radius: 6px;
border: 1px solid #dee2e6;
}
.metric-row {
display: flex;
justify-content: space-between;
margin-bottom: 15px;
padding-bottom: 15px;
border-bottom: 1px solid #eee;
}
.metric-label {
font-weight: 600;
color: #555;
}
.metric-value {
font-weight: 700;
color: #2c3e50;
}
.zone-table {
width: 100%;
border-collapse: collapse;
margin-top: 20px;
}
.zone-table th, .zone-table td {
text-align: left;
padding: 12px;
border-bottom: 1px solid #ddd;
}
.zone-table th {
background-color: #f1f3f5;
color: #495057;
}
.zone-color {
width: 15px;
height: 15px;
display: inline-block;
border-radius: 50%;
margin-right: 10px;
}
.content-section {
padding: 20px 0;
}
.content-section h2 {
color: #2c3e50;
margin-top: 30px;
}
.content-section h3 {
color: #e74c3c;
margin-top: 20px;
}
.content-section ul {
padding-left: 20px;
}
.content-section li {
margin-bottom: 10px;
}
function calculateHeartRateZones() {
// Get inputs
var ageInput = document.getElementById("inputAge").value;
var rhrInput = document.getElementById("inputRHR").value;
// Validate inputs
var age = parseFloat(ageInput);
var rhr = parseFloat(rhrInput);
if (isNaN(age) || age 120) {
alert("Please enter a valid age.");
return;
}
if (isNaN(rhr) || rhr 200) {
alert("Please enter a valid resting heart rate (typically between 30 and 100 bpm).");
return;
}
// 1. Calculate Max Heart Rate (Standard Formula)
var maxHR = 220 – age;
// 2. Calculate Heart Rate Reserve (HRR)
var hrr = maxHR – rhr;
// Display basic metrics
document.getElementById("dispMaxHR").innerHTML = maxHR + " bpm";
document.getElementById("dispHRR").innerHTML = hrr + " bpm";
// Define Zones Data
// Zones definition: [Min%, Max%, Name, Color, Description]
var zones = [
{ min: 0.50, max: 0.60, name: "Zone 1: Very Light", color: "#a8e6cf", desc: "Warm up / Recovery" },
{ min: 0.60, max: 0.70, name: "Zone 2: Light", color: "#dcedc1", desc: "Fat Burning / Endurance" },
{ min: 0.70, max: 0.80, name: "Zone 3: Moderate", color: "#ffd3b6", desc: "Aerobic Fitness" },
{ min: 0.80, max: 0.90, name: "Zone 4: Hard", color: "#ffaaa5", desc: "Anaerobic Threshold" },
{ min: 0.90, max: 1.00, name: "Zone 5: Maximum", color: "#ff8b94", desc: "Maximum Effort" }
];
var tableBody = document.getElementById("zoneBody");
tableBody.innerHTML = ""; // Clear previous results
// Loop through zones and calculate ranges using Karvonen formula
// Formula: TargetHR = (HRR * intensity) + RHR
for (var i = 0; i < zones.length; i++) {
var z = zones[i];
var lowerBPM = Math.round((hrr * z.min) + rhr);
var upperBPM = Math.round((hrr * z.max) + rhr);
var row = document.createElement("tr");
var colorBox = '';
row.innerHTML =
'' + colorBox + z.name + ' ' +
'' + (z.min * 100) + '% – ' + (z.max * 100) + '% ' +
'' + lowerBPM + ' – ' + upperBPM + ' bpm ' +
'' + z.desc + ' ';
tableBody.appendChild(row);
}
// Show results div
document.getElementById("results").style.display = "block";
}
Karvonen Heart Rate Zone Calculator
Ideally measured in the morning before getting out of bed.
Your Personal Heart Rate Profile
Estimated Max Heart Rate (MHR):
– bpm
Heart Rate Reserve (HRR):
– bpm
| Zone | Intensity | Target Range (BPM) | Benefit |
|---|
Optimizing Training with the Karvonen Formula
Training effectively requires more than just guessing your effort level. To truly improve cardiovascular health, burn fat, or increase athletic performance, you need to train in specific heart rate zones. The calculator above utilizes the Karvonen Method, which is widely considered more accurate than the standard "220 minus age" formula because it incorporates your Resting Heart Rate (RHR).
Why Resting Heart Rate Matters
The standard formula (220 – Age) assumes everyone of the same age has the same fitness level. However, a highly conditioned athlete has a much lower resting heart rate than a sedentary individual. By factoring in your RHR, the Karvonen formula calculates your Heart Rate Reserve (HRR), which is the difference between your maximum heart rate and your resting heart rate. This provides a personalized range that reflects your actual cardiovascular fitness.
Understanding Your Heart Rate Zones
Training in different zones triggers different physiological adaptations. Here is a breakdown of the 5 standard training zones calculated above:
- Zone 1 (Very Light, 50-60%): Used for warm-ups, cool-downs, and active recovery. It aids in recovery and prepares the body for more intense activity.
- Zone 2 (Light, 60-70%): Often called the "Fat Burning Zone." Training here improves general endurance and utilizes fat sources as the primary fuel. You should be able to hold a conversation easily.
- Zone 3 (Moderate, 70-80%): The aerobic zone. This improves the efficiency of blood circulation and skeletal muscles. It is the sweet spot for improving cardiovascular fitness.
- Zone 4 (Hard, 80-90%): The anaerobic threshold zone. Training here increases the amount of lactate your body can tolerate and improves high-speed endurance. It is hard to speak more than a few words.
- Zone 5 (Maximum, 90-100%): For short bursts of maximum effort (sprinting). This develops fast-twitch muscle fibers and maximum speed. Sustainable for only very short periods.
How to Measure Resting Heart Rate
For the most accurate results in the calculator above, measure your resting heart rate right after waking up in the morning, before you get out of bed or drink coffee. Count your pulse for 60 seconds, or for 15 seconds and multiply by 4. Do this for three days and take the average.
The Math Behind the Calculator
The calculation follows these steps:
- Max HR = 220 – Age
- Heart Rate Reserve (HRR) = Max HR – Resting HR
- Target Zone Lower Limit = (HRR × Min Intensity %) + Resting HR
- Target Zone Upper Limit = (HRR × Max Intensity %) + Resting HR