What is Target Heart Rate?
Your target heart rate zone is a range of your maximum heart rate that is usually expressed as a percentage. Exercising within your target heart rate zone is a good way to improve your cardiovascular fitness. The intensity of your workout determines which zone you should aim for:
- Moderate Intensity (50-70% of Maximum Heart Rate): You can talk but not sing. This zone helps improve aerobic fitness and burn fat.
- Vigorous Intensity (70-85% of Maximum Heart Rate): You can only say a few words without pausing for breath. This zone helps improve aerobic capacity and is good for high-intensity interval training (HIIT).
How is it Calculated?
The most common method to estimate your maximum heart rate (MHR) is the simple formula: 220 – Age.
For a more personalized calculation, the Karvonen Formula is used, which takes your Resting Heart Rate (RHR) into account:
Heart Rate Reserve (HRR) = MHR – RHR
Then, to find the target heart rate for a specific intensity percentage (e.g., 60%):
Target Heart Rate = (HRR * Intensity Percentage) + RHR
Example Calculation:
Let's say you are 40 years old and your resting heart rate is 65 bpm.
- Estimated Maximum Heart Rate (MHR): 220 – 40 = 180 bpm
- Heart Rate Reserve (HRR): 180 – 65 = 115 bpm
- Moderate Intensity (60%): (115 * 0.60) + 65 = 69 + 65 = 134 bpm
- Vigorous Intensity (80%): (115 * 0.80) + 65 = 92 + 65 = 157 bpm
So, for this 40-year-old individual, the target heart rate zone for moderate intensity would be approximately 134 bpm, and for vigorous intensity, around 157 bpm.
function calculateHeartRate() {
var ageInput = document.getElementById("age");
var restingHeartRateInput = document.getElementById("restingHeartRate");
var resultsDiv = document.getElementById("targetHeartRateResults");
var age = parseFloat(ageInput.value);
var restingHeartRate = parseFloat(restingHeartRateInput.value);
if (isNaN(age) || age = 120) {
resultsDiv.innerHTML = "Please enter a valid age (between 1 and 119).";
return;
}
// Estimate Maximum Heart Rate (MHR)
var maxHeartRate = 220 – age;
var heartRateReserve;
var moderateLow, moderateHigh, vigorousLow, vigorousHigh;
if (isNaN(restingHeartRate) || restingHeartRate = maxHeartRate) {
// Use estimated RHR if input is invalid or not provided
// A common estimation for RHR is around 70% of MHR for general population, but this is less accurate.
// For simplicity, we'll just use MHR if RHR is not valid.
// A better approach would be to educate the user on how to find their RHR.
heartRateReserve = maxHeartRate; // Effectively bypasses HRR for calculation if RHR is not used
moderateLow = maxHeartRate * 0.50;
moderateHigh = maxHeartRate * 0.70;
vigorousLow = maxHeartRate * 0.70;
vigorousHigh = maxHeartRate * 0.85;
resultsDiv.innerHTML = `
Estimated Maximum Heart Rate:
${maxHeartRate.toFixed(0)} bpm
(Resting Heart Rate not entered or invalid. Calculations based on Maximum Heart Rate only.)
Moderate Intensity Zone (50-70% of MHR): ${moderateLow.toFixed(0)} – ${moderateHigh.toFixed(0)} bpm
Vigorous Intensity Zone (70-85% of MHR): ${vigorousLow.toFixed(0)} – ${vigorousHigh.toFixed(0)} bpm
`;
} else {
// Use Karvonen Formula
heartRateReserve = maxHeartRate – restingHeartRate;
moderateLow = (heartRateReserve * 0.50) + restingHeartRate;
moderateHigh = (heartRateReserve * 0.70) + restingHeartRate;
vigorousLow = (heartRateReserve * 0.70) + restingHeartRate;
vigorousHigh = (heartRateReserve * 0.85) + restingHeartRate;
resultsDiv.innerHTML = `
Estimated Maximum Heart Rate:
${maxHeartRate.toFixed(0)} bpm
Your Resting Heart Rate:
${restingHeartRate.toFixed(0)} bpm
Moderate Intensity Zone (50-70% of HRR + RHR): ${moderateLow.toFixed(0)} – ${moderateHigh.toFixed(0)} bpm
Vigorous Intensity Zone (70-85% of HRR + RHR): ${vigorousLow.toFixed(0)} – ${vigorousHigh.toFixed(0)} bpm
`;
}
}
function estimateRHR() {
var ageInput = document.getElementById("age");
var restingHeartRateInput = document.getElementById("restingHeartRate");
var age = parseFloat(ageInput.value);
if (isNaN(age) || age = 120) {
alert("Please enter a valid age first.");
return;
}
// A very rough estimation of RHR. Actual measurement is always best.
// This is a simplification and not scientifically rigorous.
var estimatedRHR = Math.round((220 – age) * 0.65); // ~65% of MHR as a rough guess
if (estimatedRHR 100) estimatedRHR = 100; // Max RHR
restingHeartRateInput.value = estimatedRHR;
calculateHeartRate();
}
.heart-rate-calculator {
font-family: sans-serif;
display: flex;
flex-wrap: wrap;
gap: 30px;
margin-bottom: 20px;
}
.calculator-inputs {
flex: 1;
min-width: 300px;
border: 1px solid #eee;
padding: 20px;
border-radius: 5px;
background-color: #f9f9f9;
}
.calculator-explanation {
flex: 1;
min-width: 300px;
border: 1px solid #eee;
padding: 20px;
border-radius: 5px;
background-color: #f9f9f9;
}
.calculator-inputs h2, .calculator-explanation h3 {
color: #333;
margin-top: 0;
}
.input-group {
margin-bottom: 15px;
}
.input-group label {
display: block;
margin-bottom: 5px;
font-weight: bold;
}
.input-group input[type="number"] {
width: calc(100% – 20px);
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box; /* Include padding and border in the element's total width and height */
}
.input-group button {
margin-top: 5px;
padding: 8px 12px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
cursor: pointer;
font-size: 0.9em;
}
.input-group button:hover {
background-color: #0056b3;
}
.calculations {
margin-top: 20px;
border-top: 1px solid #eee;
padding-top: 15px;
}
.calculations h3 {
margin-top: 0;
margin-bottom: 10px;
}
#targetHeartRateResults p {
margin-bottom: 8px;
line-height: 1.5;
}
.calculator-explanation ul {
list-style-type: disc;
margin-left: 20px;
}
.calculator-explanation li {
margin-bottom: 8px;
}
.calculator-explanation strong {
color: #007bff;
}