Your heart rate, a vital sign, measures how many times your heart beats per minute (BPM). It's a key indicator of your cardiovascular health and fitness level. During exercise, your heart rate increases to supply more oxygenated blood to your working muscles. Understanding your heart rate zones allows you to tailor your workouts for specific goals, whether it's improving general fitness, burning fat, or enhancing athletic performance.
Maximum Heart Rate (MHR) Estimation
A common starting point for calculating heart rate zones is estimating your Maximum Heart Rate (MHR). The most widely used formula is the Tanaka formula:
MHR = 208 - (0.7 * Age)
While simpler formulas like 220 – Age exist, the Tanaka formula is generally considered more accurate across a wider age range.
Heart Rate Reserve (HRR)
Heart Rate Reserve (HRR) is the difference between your MHR and your Resting Heart Rate (RHR). It represents the range of heartbeats available for exercise.
HRR = MHR - RHR
Your RHR is typically measured first thing in the morning before you get out of bed, when your body is fully at rest. For this calculator, we'll use a typical resting heart rate if not provided, but for more accurate results, measuring your own RHR is recommended.
Calculating Target Heart Rate Zones
Target Heart Rate (THR) zones are calculated as a percentage of your MHR or, more accurately, as a percentage of your HRR added to your RHR. The latter method (using HRR) is often preferred as it accounts for individual fitness levels.
The general heart rate zones are:
Very Light (Recovery) Zone: 50-60% of MHR. Aids in recovery.
Hard (Anaerobic Threshold) Zone: 80-90% of MHR. Increases anaerobic capacity, boosts speed and power.
Maximum (Redline) Zone: 90-100% of MHR. Improves speed and performance for very short bursts.
This calculator will provide an estimate based on your age and selected activity intensity, using a common approach that simplifies the zone calculation. For more precise zone determination, consider using the HRR method and monitoring your actual RHR.
Example Calculation:
Let's calculate for a 30-year-old individual engaging in moderate-intensity exercise:
So, the moderate zone is approximately 131-150 BPM.
Calculate Moderate Zone (using HRR method, 70-80%):
Lower end: (0.70 * 127) + 60 = 89 + 60 = 149 BPM
Upper end: (0.80 * 127) + 60 = 102 + 60 = 162 BPM
Using the HRR method, the moderate zone is approximately 149-162 BPM. Notice the difference, highlighting the importance of RHR for accuracy.
This calculator provides a simplified estimate based on age and general intensity levels.
function calculateHeartRateZones() {
var ageInput = document.getElementById("age");
var activityLevelSelect = document.getElementById("activityLevel");
var resultValueSpan = document.getElementById("result-value");
var zoneDescriptionP = document.getElementById("zone-description");
var age = parseFloat(ageInput.value);
var activityLevel = activityLevelSelect.value;
if (isNaN(age) || age 120) {
alert("Please enter a valid age between 1 and 120.");
return;
}
// Estimate Maximum Heart Rate (MHR) using Tanaka formula
var maxHeartRate = 208 – (0.7 * age);
var lowerBound = 0;
var upperBound = 0;
var description = "";
switch (activityLevel) {
case "resting":
// Resting zone is typically just above RHR, but for simplicity, we'll show a small range around it.
// A true RHR measurement is best. We'll estimate around 50-60% of MHR for a general "active" resting state.
lowerBound = Math.round(0.50 * maxHeartRate);
upperBound = Math.round(0.60 * maxHeartRate);
description = "This zone aids in recovery and is slightly above your typical resting heart rate.";
break;
case "low":
// Light intensity: ~60-70% of MHR
lowerBound = Math.round(0.60 * maxHeartRate);
upperBound = Math.round(0.70 * maxHeartRate);
description = "Builds aerobic base and improves endurance. Feels easy.";
break;
case "moderate":
// Moderate intensity: ~70-80% of MHR
lowerBound = Math.round(0.70 * maxHeartRate);
upperBound = Math.round(0.80 * maxHeartRate);
description = "Improves cardiovascular health and fat burning efficiency. You can talk, but not sing.";
break;
case "high":
// High intensity: ~80-90% of MHR
lowerBound = Math.round(0.80 * maxHeartRate);
upperBound = Math.round(0.90 * maxHeartRate);
description = "Increases anaerobic capacity and boosts speed/power. Breathing is heavy.";
break;
default:
resultValueSpan.textContent = "–";
zoneDescriptionP.textContent = "";
return;
}
// Ensure bounds are positive
if (lowerBound < 0) lowerBound = 0;
if (upperBound < 0) upperBound = 0;
resultValueSpan.textContent = lowerBound + " – " + upperBound;
zoneDescriptionP.textContent = description;
}