Leave empty to use the standard formula instead of Karvonen.
General Health
Weight Management (Fat Burn)
Cardiovascular Endurance
Peak Performance / Speed
Please enter a valid age between 10 and 100.
Max Heart Rate
—
Heart Rate Reserve
—
Rec. Target (Avg)
—
Your Personal Heart Rate Zones
Zone
Intensity
Heart Rate Range
Benefit
*BPM = Beats Per Minute
Understanding Your Recommended Heart Rate
Monitoring your heart rate is one of the most effective ways to gauge the intensity of your workouts. Whether you are an elite athlete or just starting your fitness journey, training in the correct heart rate zone ensures you are maximizing efficiency while maintaining safety. This Recommended Heart Rate Calculator helps you determine your optimal training intensities based on your age and resting physiology.
The Science: Calculating Your Zones
There are two primary methods for calculating heart rate zones. This tool prioritizes the Karvonen Method if you provide your Resting Heart Rate, as it is generally considered more accurate for individuals with varying fitness levels.
Standard Method: Calculates zones purely based on Maximum Heart Rate (MHR). Formula: MHR = 220 - Age.
Karvonen Formula: Factors in your Resting Heart Rate (RHR) to determine Heart Rate Reserve (HRR). Formula: Target HR = ((MHR - RHR) × %Intensity) + RHR.
Heart Rate Zones Explained
Training implies targeting specific energy systems in your body. Here is a breakdown of the 5 zones calculated above:
Zone 1: Very Light (50-60%)
This is the recovery zone. It helps with warm-ups, cool-downs, and active recovery. Training here improves overall health and helps muscles recover after intense workouts.
Zone 2: Light (60-70%) – The "Fat Burn" Zone
Often cited as the best zone for weight management. In this zone, the body relies heavily on fat as a fuel source. It improves basic endurance and muscle efficiency.
Zone 3: Moderate (70-80%) – Aerobic Zone
This is where cardiovascular endurance is built. It strengthens the heart and lungs. You should be breathing harder here but still able to speak in short sentences.
Zone 4: Hard (80-90%) – Anaerobic Zone
Training in this zone improves your VO2 Max (the maximum amount of oxygen your body can utilize). It shifts the body to use carbohydrates for fuel and increases lactate tolerance.
Zone 5: Maximum (90-100%)
This zone is sustainable for only very short periods. It is used for interval training to develop speed and neuromuscular power. Consult a doctor before training in this zone.
How to Measure Resting Heart Rate
To get the most accurate results from this calculator, measure your pulse immediately after waking up in the morning, before getting out of bed. Count the beats for 60 seconds. Do this for 3-5 days and take the average.
function calculateHeartRateZones() {
// 1. Get Inputs
var ageInput = document.getElementById("userAge");
var rhrInput = document.getElementById("restingHR");
var goalInput = document.getElementById("fitnessGoal");
var resultDiv = document.getElementById("resultOutput");
var errorDiv = document.getElementById("errorDisplay");
var tableBody = document.getElementById("zonesTableBody");
var age = parseFloat(ageInput.value);
var rhr = parseFloat(rhrInput.value);
var goal = goalInput.value;
// 2. Validation
if (isNaN(age) || age 100) {
errorDiv.style.display = "block";
resultDiv.style.display = "none";
return;
} else {
errorDiv.style.display = "none";
}
// 3. Logic Setup
var maxHR = 220 – age;
var useKarvonen = !isNaN(rhr) && rhr > 0 && rhr < maxHR;
var hrr = 0;
// Display Basics
document.getElementById("displayMaxHR").innerHTML = Math.round(maxHR) + " bpm";
if (useKarvonen) {
hrr = maxHR – rhr;
document.getElementById("displayHRR").innerHTML = Math.round(hrr) + " bpm";
} else {
document.getElementById("displayHRR").innerHTML = "N/A";
// If user input invalid RHR (like 0 or higher than MaxHR), treat as standard
rhr = 0;
hrr = maxHR; // For standard calc math: (MHR * %) is same as ((MHR-0)*%) + 0
}
// 4. Define Zones
var zones = [
{ id: 1, minPct: 0.50, maxPct: 0.60, name: "Very Light", benefit: "Warm up, Recovery", colorClass: "zone-row-1" },
{ id: 2, minPct: 0.60, maxPct: 0.70, name: "Light", benefit: "Fat Burning, Endurance", colorClass: "zone-row-2" },
{ id: 3, minPct: 0.70, maxPct: 0.80, name: "Moderate", benefit: "Aerobic Fitness", colorClass: "zone-row-3" },
{ id: 4, minPct: 0.80, maxPct: 0.90, name: "Hard", benefit: "Anaerobic Capacity", colorClass: "zone-row-4" },
{ id: 5, minPct: 0.90, maxPct: 1.00, name: "Maximum", benefit: "Speed, Power", colorClass: "zone-row-5" }
];
// 5. Generate Table HTML
var tableHTML = "";
var recTargetLow = 0;
var recTargetHigh = 0;
// Determine recommended zone based on goal
var targetZoneId = 3; // Default
if(goal === "fatloss") targetZoneId = 2;
if(goal === "cardio") targetZoneId = 3;
if(goal === "performance") targetZoneId = 4;
if(goal === "general") targetZoneId = 1;
for (var i = 0; i < zones.length; i++) {
var z = zones[i];
// Calculate BPM range
// Standard: MaxHR * Pct
// Karvonen: (HRR * Pct) + RHR
var minBPM, maxBPM;
if (useKarvonen) {
minBPM = Math.round((hrr * z.minPct) + rhr);
maxBPM = Math.round((hrr * z.maxPct) + rhr);
} else {
minBPM = Math.round(maxHR * z.minPct);
maxBPM = Math.round(maxHR * z.maxPct);
}
// Capture target for summary box
if (z.id === targetZoneId) {
recTargetLow = minBPM;
recTargetHigh = maxBPM;
} else if (goal === "general" && z.id === 2) {
// For general, maybe average zone 1 and 2, but let's stick to 1-2
recTargetHigh = maxBPM; // extend range
}
// Styling for active goal
var rowStyle = (z.id === targetZoneId) ? "background-color: #fff8e1; font-weight:bold;" : "";
var highlight = (z.id === targetZoneId) ? " ★ GOAL" : "";
tableHTML += "