Measure this in the morning before getting out of bed.
If you know your actual Max HR from a field test, enter it here.
Estimated Max Heart Rate:–
Heart Rate Reserve (HRR):–
Target "Easy Run" Zone
– BPM
(60% – 70% of Heart Rate Reserve)
Why Calculate Your Easy Run Pace?
Many runners make the mistake of running their "easy" days too hard. This accumulates fatigue without providing the specific aerobic benefits of low-intensity training. Using an Easy Run Heart Rate Calculator ensures you stay in the optimal physiological zone to build endurance, increase mitochondrial density, and recover from hard sessions.
The Karvonen Formula vs. Standard Formula
This calculator uses the Karvonen Method (Heart Rate Reserve), which is generally considered more accurate for athletes than the basic "220 minus age" formula. The standard formula assumes a generic decline in heart rate max but ignores your fitness level.
The Karvonen formula incorporates your Resting Heart Rate (RHR). A lower RHR typically indicates better cardiovascular fitness. By using your Heart Rate Reserve (Max HR minus Resting HR), the training zones are scaled specifically to your available heart rate capacity.
Understanding the Zones
Easy Run (Zone 2): Typically 60% to 70% of your Heart Rate Reserve. This is a conversational pace where you can speak in full sentences. It builds your aerobic base.
Aerobic/Tempo (Zone 3): 70% to 80% of HRR. Harder, breathing is rhythmic but not gasping.
Threshold (Zone 4): 80% to 90% of HRR. "Comfortably hard" running.
How to Use These Numbers
Once you have your range (e.g., 135-148 BPM), wear a heart rate monitor during your recovery or long slow distance runs. If your heart rate spikes above the upper limit, slow down or walk until it drops back into the zone. Discipline in keeping your easy runs truly easy is the secret to running faster on race day.
Example Calculation
For a 30-year-old runner with a resting heart rate of 50 BPM:
Max HR: 190 (estimated as 220 – 30)
Heart Rate Reserve: 140 (190 – 50)
60% Intensity: (140 × 0.60) + 50 = 134 BPM
70% Intensity: (140 × 0.70) + 50 = 148 BPM
Easy Run Zone: 134 to 148 BPM
function calculateEasyRun() {
// Get inputs
var ageInput = document.getElementById("runnerAge").value;
var rhrInput = document.getElementById("restingHR").value;
var maxHrInput = document.getElementById("maxHR").value;
// Clean values
var age = parseFloat(ageInput);
var rhr = parseFloat(rhrInput);
var maxHr = parseFloat(maxHrInput);
// Validation
if (isNaN(age) || age < 1) {
alert("Please enter a valid age.");
return;
}
if (isNaN(rhr) || rhr 150) {
alert("Please enter a valid Resting Heart Rate (typically between 30 and 100).");
return;
}
// Logic: Max HR
var calculatedMax = 0;
var isEstimated = false;
if (!isNaN(maxHr) && maxHr > 0) {
calculatedMax = maxHr;
} else {
// Tanaka formula is 208 – (0.7 * age), but standard 220-age is requested/common for general use
// We will use 220 – Age for simplicity as per common standard, or implied context
calculatedMax = 220 – age;
isEstimated = true;
}
// Validation for Max HR vs Resting
if (calculatedMax <= rhr) {
alert("Your Max Heart Rate must be higher than your Resting Heart Rate. Please check your inputs.");
return;
}
// Logic: Heart Rate Reserve (HRR)
var hrr = calculatedMax – rhr;
// Logic: Easy Run Zones (Zone 2: 60% – 70% of HRR + RHR)
// Formula: Target HR = (HRR * %Intensity) + RHR
var zoneLowerPercent = 0.60;
var zoneUpperPercent = 0.70;
var lowerBound = Math.round((hrr * zoneLowerPercent) + rhr);
var upperBound = Math.round((hrr * zoneUpperPercent) + rhr);
// Display Results
var resultContainer = document.getElementById("resultsArea");
var dispMax = document.getElementById("dispMaxHR");
var dispHrr = document.getElementById("dispHRR");
var dispZone = document.getElementById("zoneRange");
dispMax.innerHTML = Math.round(calculatedMax) + " BPM" + (isEstimated ? " (Estimated)" : "");
dispHrr.innerHTML = Math.round(hrr) + " BPM";
dispZone.innerHTML = lowerBound + " – " + upperBound + " BPM";
// Show container
resultContainer.style.display = "block";
}