Leave blank to use the standard formula. Enter value for Karvonen formula accuracy.
Maximum Heart Rate (MHR):185 BPM
Fat Burning Zone (60-70%):111 – 130 BPM
Aerobic / Cardio Zone (70-80%):130 – 148 BPM
Calculation based on the standard 220-Age formula.
Optimizing Fat Loss Through Heart Rate Training
Understanding your heart rate zones is one of the most effective ways to maximize the efficiency of your workouts. While simply moving your body is beneficial, targeting specific heart rate intensities can shift your body's metabolism to prioritize burning fat over carbohydrates for fuel. This Exercise Heart Rate Calculator helps you identify the "sweet spot" known as the Fat Burning Zone.
What is the Fat Burning Zone?
The Fat Burning Zone is a specific range of heart rate intensity, typically between 60% and 70% of your Maximum Heart Rate (MHR). At this lower intensity, your body has enough oxygen available to oxidize fat molecules for energy. As intensity increases beyond this point (into the cardio or anaerobic zones), your body switches to burning glycogen (stored carbohydrates) because it requires a faster energy source.
Zone
Intensity (% of MHR)
Primary Benefit
Warm Up
50-60%
Health & Recovery
Fat Burning
60-70%
Fat Metabolism & Endurance
Aerobic (Cardio)
70-80%
Cardiovascular Fitness
Anaerobic
80-90%
Performance & Speed
Standard MHR vs. The Karvonen Formula
This calculator employs two methods depending on the data you provide:
Standard Method: Uses the simple equation 220 – Age to estimate your maximum heart rate. This provides a general baseline suitable for beginners.
Karvonen Formula: If you input your Resting Heart Rate (RHR), the calculator uses the Karvonen method. This is considered more accurate for individuals with varying fitness levels because it takes into account your Heart Rate Reserve (HRR). The formula is: Target HR = ((Max HR - Resting HR) × %Intensity) + Resting HR.
How to Measure Your Resting Heart Rate
To get the most accurate result from the Karvonen formula, measure your pulse immediately after waking up in the morning, before getting out of bed. Count the beats for 60 seconds. A lower resting heart rate generally indicates better cardiovascular fitness.
Tips for Training in the Fat Burning Zone
Training in this zone feels relatively easy; you should be able to carry on a conversation without gasping for breath. Consistency is key:
Duration Matters: Since the intensity is lower, aim for longer sessions (45-60 minutes) to burn a significant total number of calories.
Monitor Your Pulse: Use a smartwatch, chest strap, or manual pulse check during exercise to ensure you stay within the BPM range provided by the calculator.
Mix It Up: While the fat burning zone uses a higher percentage of fat for fuel, high-intensity intervals (HIIT) can burn more total calories. A balanced routine often includes both.
function calculateFatBurn() {
var ageInput = document.getElementById('ageInput');
var rhrInput = document.getElementById('rhrInput');
var resultContainer = document.getElementById('resultContainer');
var mhrDisplay = document.getElementById('mhrResult');
var fatBurnDisplay = document.getElementById('fatBurnZoneResult');
var cardioDisplay = document.getElementById('cardioZoneResult');
var methodDisplay = document.getElementById('methodUsed');
var age = parseFloat(ageInput.value);
var rhr = parseFloat(rhrInput.value);
// Validation
if (isNaN(age) || age 120) {
alert("Please enter a valid age between 1 and 120.");
return;
}
// Calculate Max Heart Rate (Standard 220-Age)
var mhr = 220 – age;
var fatBurnLow, fatBurnHigh, cardioLow, cardioHigh;
var isKarvonen = false;
// Check if RHR is provided and valid
if (!isNaN(rhr) && rhr > 30 && rhr < 150) {
isKarvonen = true;
// Karvonen Formula: Target = ((MHR – RHR) * %) + RHR
var hrr = mhr – rhr; // Heart Rate Reserve
fatBurnLow = Math.round((hrr * 0.60) + rhr);
fatBurnHigh = Math.round((hrr * 0.70) + rhr);
cardioLow = Math.round((hrr * 0.70) + rhr);
cardioHigh = Math.round((hrr * 0.80) + rhr);
} else {
// Standard Formula: Target = MHR * %
fatBurnLow = Math.round(mhr * 0.60);
fatBurnHigh = Math.round(mhr * 0.70);
cardioLow = Math.round(mhr * 0.70);
cardioHigh = Math.round(mhr * 0.80);
}
// Update DOM
mhrDisplay.innerHTML = mhr + " BPM";
fatBurnDisplay.innerHTML = fatBurnLow + " – " + fatBurnHigh + " BPM";
cardioDisplay.innerHTML = cardioLow + " – " + cardioHigh + " BPM";
if (isKarvonen) {
methodDisplay.innerHTML = "Calculation based on the Karvonen Formula (incorporating resting heart rate).";
} else {
methodDisplay.innerHTML = "Calculation based on the standard 220-Age formula. Enter Resting HR for more precision.";
}
// Show results
resultContainer.style.display = "block";
// Scroll to results on mobile
resultContainer.scrollIntoView({behavior: "smooth", block: "nearest"});
}