Calculating your target heart rate is essential for optimizing your cardiovascular workouts. Whether your goal is fat loss, endurance building, or maximum performance, training in the correct "zone" ensures you are stimulating your cardiovascular system effectively without overtraining.
The Karvonen Formula vs. Standard Method
This calculator utilizes the Karvonen Formula, which is widely considered more accurate than the standard "220 minus age" method for determining exercise intensity. The standard method assumes a linear relationship that doesn't account for individual fitness levels.
The Karvonen Formula incorporates your Resting Heart Rate (RHR) into the equation. By calculating your Heart Rate Reserve (HRR)—the difference between your maximum and resting heart rates—we can determine target zones that are tailored to your specific physiology.
Zone 1 (50-60% – Warm Up / Recovery): Very light intensity. Ideal for warming up, cooling down, or active recovery days. It improves overall health and helps recovery.
Zone 2 (60-70% – Fat Burning): Light intensity. This zone trains your body to be more efficient at using fat as a fuel source. It builds basic endurance.
Zone 3 (70-80% – Aerobic): Moderate intensity. Often called the "sweet spot" for training. It improves aerobic capacity and blood circulation.
Zone 4 (80-90% – Anaerobic): Hard intensity. You start to feel the burn as your body produces lactic acid. This improves speed and power.
Zone 5 (90-100% – Maximum): Maximum effort. Sustainable only for very short bursts. Used for interval training to improve peak performance.
Why Resting Heart Rate Matters
Your resting heart rate is a strong indicator of your cardiovascular health. A lower RHR typically indicates a stronger, more efficient heart and higher aerobic fitness. As you get fitter, your RHR will likely decrease, changing your Heart Rate Reserve and shifting your training zones. It is recommended to recalculate your zones every few months as your fitness level changes.
function calculateHeartRateZones() {
// 1. Get Inputs
var ageInput = document.getElementById('ehr-age');
var rhrInput = document.getElementById('ehr-rhr');
var resultContainer = document.getElementById('ehr-result');
var age = parseFloat(ageInput.value);
var rhr = parseFloat(rhrInput.value);
// 2. Validation
if (isNaN(age) || age 120) {
alert("Please enter a valid age between 1 and 120.");
return;
}
if (isNaN(rhr) || rhr 200) {
alert("Please enter a valid resting heart rate (typically between 40-100 BPM).");
return;
}
// 3. Calculation Logic (Karvonen)
var maxHR = 220 – age;
var hrr = maxHR – rhr; // Heart Rate Reserve
// Safety check
if (hrr <= 0) {
alert("Calculated Maximum Heart Rate is lower than Resting Heart Rate. Please check your inputs.");
return;
}
// Function to calculate specific intensity
function calcZone(percentage) {
return Math.round((hrr * percentage) + rhr);
}
// 4. Generate Output HTML
var outputHTML = '';
// Summary Statistics
outputHTML += '