Measure this in the morning before getting out of bed.
Your Weight Loss Zone
To maximize fat burning, keep your heart rate between:
Beats Per Minute (BPM)
How to Calculate Heart Rate for Weight Loss
If your goal is shedding pounds, understanding your "Fat Burning Zone" is a game-changer. While any movement burns calories, exercising at a specific intensity ensures that a higher percentage of those calories come from stored fat rather than glycogen (carbohydrates).
Understanding the Fat Burning Zone
The fat-burning zone typically falls between 60% and 70% of your maximum heart rate (MHR). At this moderate intensity, your body can efficiently use oxygen to metabolize fat. When you push into higher intensity zones (75%+), your body switches to burning sugar because it's a faster energy source.
The Karvonen Formula: A Better Way to Calculate
Most basic charts only use age. However, the Karvonen Formula is more accurate because it factors in your Resting Heart Rate (RHR). This accounts for your current fitness level. To use the Karvonen Formula, you first find your Heart Rate Reserve (HRR):
The Math:
1. Max HR = 220 – Age
2. Heart Rate Reserve (HRR) = Max HR – Resting HR
3. Target HR = (HRR × Intensity%) + Resting HR
Step-by-Step Example
Let's say you are 40 years old with a resting heart rate of 70 BPM. You want to exercise at 60% intensity for fat loss:
Max HR: 220 – 40 = 180 BPM
HRR: 180 – 70 = 110 BPM
Lower Limit (60%): (110 × 0.60) + 70 = 136 BPM
Upper Limit (70%): (110 × 0.70) + 70 = 147 BPM
In this example, your ideal range for weight loss is 136 to 147 beats per minute.
Why Resting Heart Rate Matters
An athlete with a resting heart rate of 50 BPM has a different physiological response to exercise than someone with a resting rate of 85 BPM. By including your RHR, you ensure the calculator provides a personalized target that isn't too easy or dangerously intense.
How to Monitor Your Heart Rate
The most effective way to track your intensity is with a chest strap or a smartwatch. If you don't have one, you can manually check your pulse at your wrist (radial artery) for 15 seconds and multiply by four. If you find yourself gasping for air, you've likely exited the fat-burning zone and entered the anaerobic zone.
function calculateFatBurningZone() {
var age = document.getElementById('hrAge').value;
var resting = document.getElementById('hrResting').value;
var resultDiv = document.getElementById('hrResult');
var rangeDisplay = document.getElementById('hrRange');
var summaryDisplay = document.getElementById('hrSummary');
if (!age || age 120) {
alert("Please enter a valid age.");
return;
}
var ageNum = parseFloat(age);
var maxHR = 220 – ageNum;
var restingNum = resting ? parseFloat(resting) : 0;
var lowBPM, highBPM;
if (restingNum > 0) {
// Karvonen Formula
var hrr = maxHR – restingNum;
lowBPM = Math.round((hrr * 0.60) + restingNum);
highBPM = Math.round((hrr * 0.70) + restingNum);
summaryDisplay.innerHTML = "Based on the Karvonen Formula, considering your resting heart rate of " + restingNum + " BPM.";
} else {
// Simple Percentage Method
lowBPM = Math.round(maxHR * 0.60);
highBPM = Math.round(maxHR * 0.70);
summaryDisplay.innerHTML = "Based on the standard Age-based formula. Add your resting heart rate for better accuracy.";
}
rangeDisplay.innerHTML = lowBPM + " – " + highBPM;
resultDiv.style.display = 'block';
// Smooth scroll to result
resultDiv.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}