Use this calculator to determine your Heart Rate Reserve (HRR) and find your target training heart rate based on the Karvonen formula. This method accounts for your individual resting heart rate, providing a more accurate training zone than standard maximum heart rate calculations.
Best measured immediately upon waking up.
Moderate exercise is typically 50-70%, vigorous is 70-85%.
function calculateHRR() {
var ageStr = document.getElementById('ageInput').value;
var rhrStr = document.getElementById('rhrInput').value;
var intensityStr = document.getElementById('intensityInput').value;
var age = parseFloat(ageStr);
var rhr = parseFloat(rhrStr);
var intensity = parseFloat(intensityStr);
var resultDiv = document.getElementById('hrrResult');
if (isNaN(age) || age <= 0 || isNaN(rhr) || rhr <= 0 || isNaN(intensity) || intensity 100) {
resultDiv.innerHTML = 'Please enter valid positive numbers for age and resting heart rate, and an intensity percentage between 1 and 100.';
return;
}
// Estimate Maximum Heart Rate (MHR) using standard 220-age formula
var mhr = 220 – age;
// Calculate Heart Rate Reserve (HRR)
var hrr = mhr – rhr;
if (hrr <= 0) {
resultDiv.innerHTML = 'The combination of age and resting heart rate provided results in an invalid Heart Rate Reserve. Please check your inputs.';
return;
}
// Calculate Target Heart Rate (THR) using Karvonen formula: (HRR * intensity%) + RHR
var intensityDecimal = intensity / 100;
var thr = (hrr * intensityDecimal) + rhr;
var resultHTML = '
Results based on Karvonen Method
';
resultHTML += '
Estimated Max Heart Rate (MHR):' + Math.round(mhr) + ' bpm
In the world of cardiovascular fitness and exercise prescription, Heart Rate Reserve (HRR) is a crucial metric used to calculate personalized and accurate Target Heart Rate (THR) training zones.
While many basic formulas simply take a percentage of your estimated maximum heart rate (MHR), these basic methods ignore a vital component of your individual fitness: your resting heart rate. HRR bridges this gap, providing a more tailored approach to gauging exercise intensity.
Defining Heart Rate Reserve (HRR)
Heart Rate Reserve is effectively the functional range of your heart. It represents the number of beats per minute available to you between when you are completely at rest and when your heart is working at its absolute maximum capacity.
HRR is used because it accounts for fitness levels. A highly conditioned athlete will have a significantly lower resting heart rate than a sedentary individual of the same age.
Example A (Sedentary): A 40-year-old with a resting heart rate of 80 bpm. Their estimated MHR is 180 (220-40). Their HRR is 100 bpm (180 – 80).
Example B (Athlete): A 40-year-old with a resting heart rate of 50 bpm. Their estimated MHR is still 180. However, their HRR is 130 bpm (180 – 50).
The athlete has a larger "reserve" of heartbeats to utilize during exercise.
The Karvonen Formula: Calculating Target Heart Rate
Once the HRR is determined, it is almost exclusively used in the Karvonen Formula to calculate target training zones. This method ensures that the training intensity percentage is applied only to the "reserve" beats, and then the resting baseline is added back in.
By using HRR in this calculation, you ensure that 50% intensity actually feels like 50% effort for your body, regardless of whether your resting rate is high or low. The calculator above uses this exact method to help you define your optimal training zones for goals ranging from fat burning to aerobic endurance and anaerobic conditioning.