Check your Health app > Heart > Resting Heart Rate.
Only enter if you have a medically tested Max HR.
Estimated Max HR:0 BPM |
Heart Rate Reserve:0 BPM
Zone 1Recovery (50-60%)
—
Zone 2Aerobic Base (60-70%)
—
Zone 3Tempo (70-80%)
—
Zone 4Threshold (80-90%)
—
Zone 5Anaerobic (90-100%)
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function calculateAppleZones() {
// Get input values
var ageInput = document.getElementById('af_age');
var rhrInput = document.getElementById('af_rhr');
var maxHrInput = document.getElementById('af_max_hr');
var age = parseFloat(ageInput.value);
var rhr = parseFloat(rhrInput.value);
var manualMax = parseFloat(maxHrInput.value);
// Validation
if (isNaN(age) || age < 1 || isNaN(rhr) || rhr 0) {
maxHR = manualMax;
} else {
// Standard formula often used as default baseline
maxHR = 220 – age;
}
// Calculate Heart Rate Reserve (Karvonen Method / Apple Pro Logic)
var hrr = maxHR – rhr;
// Display Meta Data
document.getElementById('disp_max_hr').textContent = Math.round(maxHR);
document.getElementById('disp_hrr').textContent = Math.round(hrr);
// Calculation Function for ranges
// Formula: (HRR * Percentage) + RHR
function getZoneLimit(percentage) {
return Math.round((hrr * percentage) + rhr);
}
// Zone 1: 50% – 60%
var z1_low = getZoneLimit(0.50);
var z1_high = getZoneLimit(0.60) – 1; // Subtract 1 to avoid overlap with next zone start
// Zone 2: 60% – 70%
var z2_low = getZoneLimit(0.60);
var z2_high = getZoneLimit(0.70) – 1;
// Zone 3: 70% – 80%
var z3_low = getZoneLimit(0.70);
var z3_high = getZoneLimit(0.80) – 1;
// Zone 4: 80% – 90%
var z4_low = getZoneLimit(0.80);
var z4_high = getZoneLimit(0.90) – 1;
// Zone 5: 90% – 100%
var z5_low = getZoneLimit(0.90);
var z5_high = maxHR;
// Update DOM
document.getElementById('z1_range').textContent = z1_low + " – " + z1_high + " BPM";
document.getElementById('z2_range').textContent = z2_low + " – " + z2_high + " BPM";
document.getElementById('z3_range').textContent = z3_low + " – " + z3_high + " BPM";
document.getElementById('z4_range').textContent = z4_low + " – " + z4_high + " BPM";
document.getElementById('z5_range').textContent = z5_low + " – " + z5_high + " BPM";
// Show Results
document.getElementById('results-area').style.display = 'block';
}
How Does Apple Fitness Calculate Heart Rate Zones?
Since the release of watchOS 9, Apple Watch has provided native Heart Rate Zone tracking within the Workout app. Understanding how these zones are calculated is essential for athletes aiming to optimize their training, whether for fat loss (Zone 2) or peak performance (Zone 5).
The Heart Rate Reserve (HRR) Method
While basic fitness trackers often use a simple percentage of your Maximum Heart Rate (Max HR), Apple Fitness defaults to the Heart Rate Reserve (HRR) method if you have entered your birthdate and the watch has recorded a Resting Heart Rate (RHR).
The HRR method is considered more accurate for individuals with varying fitness levels because it accounts for your cardiovascular efficiency (your resting heart rate). The formula used is:
Max HR: Generally calculated as 220 minus your age, though Apple may adjust this automatically based on historical workout data.
Resting HR (RHR): The average heart rate when you are inactive. A lower RHR typically indicates better cardiovascular fitness.
Apple segments intensity into five distinct zones. Here is what happens to your body in each:
Zone 1 (Recovery): Very light effort. Used for warm-ups and cool-downs.
Zone 2 (Aerobic Base): Often called the "fat burning" zone. You should be able to hold a conversation comfortably. This is crucial for building endurance.
Zone 3 (Tempo): Moderate effort. Breathing becomes heavier, and it becomes harder to talk. Improves aerobic efficiency.
Zone 4 (Threshold): Hard effort. You are exercising near your lactate threshold. Sustainable for shorter periods.
Zone 5 (Anaerobic): Maximum effort. Very taxing and usually sustainable only for sprints or very short intervals.
How to Customize Zones on Apple Watch
If the automatic calculations do not feel right, or if you have had a metabolic test done in a lab, you can manually edit these zones in the Watch app on your iPhone:
Open the Watch app on your iPhone.
Go to Workout > Heart Rate Zones.
Select Manual and enter your specific BPM ranges for each zone.
Using the calculator above allows you to preview what your zones should look like based on the standard Karvonen (HRR) formula used by Apple, helping you verify if your watch data is aligned with your current fitness metrics.