Calculate your Max HR and Target Zones using the Karvonen Formula.
Your Heart Rate Data
Estimated Max Heart Rate:0
Heart Rate Reserve (HRR):0
Specific Target HR (@0%):0
Target Intensity Zones
Intensity
Target BPM
Moderate (50-70%)
—
Vigorous (70-85%)
—
Peak (>85%)
—
Understanding the Heart Rate Formula
Monitoring your heart rate is one of the most effective ways to gauge the intensity of your cardiovascular exercise. By staying within specific "zones," you can tailor your workout to burn fat, improve aerobic capacity, or increase peak athletic performance. This heart rate formula calculator uses two primary methods to help you find your numbers: the Fox Formula and the Karvonen Formula.
The Formulas Explained
1. Maximum Heart Rate (MHR): The most common way to estimate MHR is the Fox Formula: 220 - Age. While simple, it provides a general baseline for the average person.
2. The Karvonen Formula: This is the method used in our calculator because it is more personalized. It takes your Resting Heart Rate (RHR) into account. The formula follows these steps:
Determine Max HR: 220 – Age.
Determine Heart Rate Reserve (HRR): Max HR – Resting HR.
A lower resting heart rate usually indicates better cardiovascular fitness. By including your RHR in the Karvonen formula, the calculator adjusts your target zones to reflect your current fitness level, preventing you from over-exerting or under-training.
Heart Rate Zones for Fitness Goals
Depending on your health goals, you should aim for different heart rate percentages:
Healthy Heart Zone (50% – 60%): Ideal for beginners or warm-ups.
Weight Management Zone (60% – 70%): Often called the "fat-burn" zone where the body utilizes a higher percentage of calories from fat.
Aerobic Zone (70% – 80%): Improves your cardiovascular system and increases lung capacity.
Anaerobic Zone (80% – 90%): Improves your VO2 Max and lactate threshold.
Example Calculation
Imagine a 40-year-old individual with a resting heart rate of 60 BPM who wants to exercise at 75% intensity:
Max HR: 220 – 40 = 180 BPM.
HRR: 180 – 60 = 120 BPM.
Target HR: (120 × 0.75) + 60 = 150 BPM.
Stay safe: Always consult with a healthcare professional before starting a new vigorous exercise program, especially if you have pre-existing heart conditions.
function calculateHeartRates() {
var age = parseFloat(document.getElementById('ageInput').value);
var rhr = parseFloat(document.getElementById('rhrInput').value);
var intensity = parseFloat(document.getElementById('intensityInput').value);
if (isNaN(age) || age 120) {
alert("Please enter a valid age.");
return;
}
if (isNaN(rhr) || rhr 150) {
alert("Please enter a valid resting heart rate (typical range 30-150).");
return;
}
if (isNaN(intensity) || intensity 100) {
alert("Please enter an intensity between 1 and 100.");
return;
}
// Calculations
var mhr = 220 – age;
var hrr = mhr – rhr;
// Check if HRR is valid (if RHR is higher than MHR)
if (hrr " + Math.round(peakLow) + " BPM";
document.getElementById('hrResults').style.display = 'block';
}