If you know your max HR from a stress test or WHOOP data, enter it here for better accuracy.
0 BPM
Estimated Maximum Heart Rate
Zone
Intensity (%)
Heart Rate Range (BPM)
Physiological Benefit
How Does WHOOP Calculate Heart Rate Zones?
Understanding your physiological data is key to improving fitness and recovery. WHOOP calculates heart rate zones primarily based on your Maximum Heart Rate (Max HR). Unlike generic trackers that might stick rigidly to the "220 minus age" formula, WHOOP is dynamic. It initially estimates your Max HR using your age but adjusts this baseline as it gathers real-time data from your workouts and daily strain.
The WHOOP Zone Methodology
WHOOP divides your heart rate intensity into 5 distinct zones. These zones are calculated as a percentage of your Max HR. Time spent in each zone contributes differently to your daily Strain score.
Zone 1 (50-60% Max HR): Very light activity. This is often active recovery, warm-ups, or cool-downs. It aids in recovery without adding significant fatigue.
Zone 2 (60-70% Max HR): The "fat burning" zone. This builds a solid aerobic base and improves endurance. You should be able to hold a conversation here.
Zone 3 (70-80% Max HR): Aerobic zone. This improves blood circulation and skeletal muscle efficiency. Breathing becomes harder, but it's sustainable for moderate durations.
Zone 4 (80-90% Max HR): Anaerobic threshold. Training here improves your ability to sustain high-speed efforts and increases lactate tolerance. It is hard work.
Zone 5 (90-100% Max HR): Peak performance. This is your maximum effort, sustainable only for very short bursts (sprints, HIIT). It develops maximum speed and power.
Why Max Heart Rate Matters
Your zones are only as accurate as your Max HR. If WHOOP thinks your Max HR is 180, but it's actually 195, your zones will be set too low, and your Strain score might be inflated because the device thinks you are working harder than you actually are. Conversely, if your Max HR is set too high, your efforts might be under-recognized.
Dynamic Adjustments
One of the defining features of WHOOP is its ability to update your Max HR automatically. If you perform a high-intensity workout and reach a heart rate higher than your currently recorded Max HR, WHOOP will update your profile and recalibrate your zones accordingly for future activities.
Improving Zone Accuracy
To ensure your zones are accurate, ensure your strap is tight and positioned correctly (about one inch above the wrist bone) to capture accurate readings during high intensity. Alternatively, using a bicep band or the WHOOP Body apparel often yields the most precise optical heart rate data during intense movement.
function calculateWhoopZones() {
var ageInput = document.getElementById('userAge');
var customMaxInput = document.getElementById('customMaxHR');
var resultsArea = document.getElementById('results-area');
var displayMaxHR = document.getElementById('displayMaxHR');
var tableBody = document.getElementById('zoneTableBody');
var age = parseFloat(ageInput.value);
var customMax = parseFloat(customMaxInput.value);
var maxHR = 0;
// Validation
if (isNaN(age) && isNaN(customMax)) {
alert("Please enter your age or a known Max Heart Rate.");
return;
}
// Logic: Use Custom Max HR if provided, otherwise estimate using 220 – Age
if (!isNaN(customMax) && customMax > 0) {
maxHR = customMax;
} else {
// Standard formula often used as baseline
maxHR = 220 – age;
}
// Safety check for unrealistic numbers
if (maxHR 250) {
alert("The calculated Max Heart Rate seems unrealistic (must be between 100 and 250 BPM). Please check your inputs.");
return;
}
displayMaxHR.innerHTML = Math.round(maxHR) + " BPM";
resultsArea.style.display = "block";
// Zone Calculations
// WHOOP Zones:
// Z5: 90-100%
// Z4: 80-90%
// Z3: 70-80%
// Z2: 60-70%
// Z1: 50-60%
var zones = [
{
name: "Zone 5",
percent: "90% – 100%",
min: Math.round(maxHR * 0.90),
max: Math.round(maxHR * 1.0),
desc: "Peak Effort / Power",
cls: "zone-5"
},
{
name: "Zone 4",
percent: "80% – 90%",
min: Math.round(maxHR * 0.80),
max: Math.round(maxHR * 0.90),
desc: "Hard / Anaerobic",
cls: "zone-4"
},
{
name: "Zone 3",
percent: "70% – 80%",
min: Math.round(maxHR * 0.70),
max: Math.round(maxHR * 0.80),
desc: "Moderate / Aerobic",
cls: "zone-3"
},
{
name: "Zone 2",
percent: "60% – 70%",
min: Math.round(maxHR * 0.60),
max: Math.round(maxHR * 0.70),
desc: "Light / Fat Burn",
cls: "zone-2"
},
{
name: "Zone 1",
percent: "50% – 60%",
min: Math.round(maxHR * 0.50),
max: Math.round(maxHR * 0.60),
desc: "Very Light / Recovery",
cls: "zone-1"
}
];
// Generate Table HTML
var html = "";
for (var i = 0; i < zones.length; i++) {
var z = zones[i];
html += "