Leave blank to use the standard age-based method. Enter for Karvonen formula.
Your Results
Estimated Max Heart Rate:— bpm
Minimum Target (50% Intensity):— bpm
Moderate Intensity (60-70%):— bpm
Vigorous Intensity (70-85%):— bpm
function calculateHeartRate() {
// Get inputs
var ageInput = document.getElementById('inputAge').value;
var rhrInput = document.getElementById('inputRestingHR').value;
// Parse inputs
var age = parseFloat(ageInput);
var rhr = parseFloat(rhrInput);
// Validation
if (isNaN(age) || age 120) {
alert("Please enter a valid age.");
return;
}
var maxHR = 220 – age;
var minTarget, modStart, modEnd, vigStart, vigEnd;
var methodText = "";
// Check if Resting Heart Rate is provided (Karvonen Formula)
if (!isNaN(rhr) && rhr > 0) {
// Karvonen Formula: TargetHR = ((MaxHR – RestingHR) * %Intensity) + RestingHR
var hrr = maxHR – rhr; // Heart Rate Reserve
minTarget = Math.round((hrr * 0.50) + rhr);
var modStartVal = Math.round((hrr * 0.60) + rhr);
var modEndVal = Math.round((hrr * 0.70) + rhr);
var vigStartVal = Math.round((hrr * 0.70) + rhr); // Overlap slightly or start at 70
var vigEndVal = Math.round((hrr * 0.85) + rhr);
modStart = modStartVal;
modEnd = modEndVal;
vigStart = vigStartVal;
vigEnd = vigEndVal;
methodText = "Calculation based on the Karvonen Formula (considering resting heart rate).";
} else {
// Standard Formula: TargetHR = MaxHR * %Intensity
minTarget = Math.round(maxHR * 0.50);
modStart = Math.round(maxHR * 0.60);
modEnd = Math.round(maxHR * 0.70);
vigStart = Math.round(maxHR * 0.70);
vigEnd = Math.round(maxHR * 0.85);
methodText = "Calculation based on the Standard Method (220 – Age). For greater accuracy, enter your resting heart rate.";
}
// Display Results
document.getElementById('dispMaxHR').innerHTML = maxHR + " bpm";
document.getElementById('dispMinTarget').innerHTML = minTarget + " bpm";
document.getElementById('dispModTarget').innerHTML = modStart + " – " + modEnd + " bpm";
document.getElementById('dispVigTarget').innerHTML = vigStart + " – " + vigEnd + " bpm";
document.getElementById('methodUsedText').innerHTML = methodText;
document.getElementById('thrResult').style.display = "block";
}
How to Calculate Minimum Target Heart Rate
Understanding your heart rate zones is essential for effective cardiovascular training. Whether you are just starting a fitness journey or looking to optimize fat burn, knowing how to calculate your minimum target heart rate ensures you are exercising at an intensity sufficient to improve your health without overexerting yourself.
Why Calculate Minimum Target Heart Rate?
Your "Minimum Target Heart Rate" generally corresponds to 50% of your maximum heart rate (or heart rate reserve). This is the entry point into the aerobic training zone. Exercising at or above this level helps to:
Warm up safely: Prepares the cardiovascular system for more intense activity.
Aid recovery: Promotes blood flow to muscles on active recovery days.
Burn fat: Lower intensity zones utilize fat as a primary fuel source.
Build endurance: Establishes a base level of aerobic fitness for beginners.
The Math Behind the Calculator
There are two primary methods used to calculate these zones. Our calculator above switches automatically depending on the data you provide.
1. The Standard Method (Fox Formula)
This is the simplest way to estimate heart rate zones but is slightly less personalized because it does not account for your fitness level (resting heart rate).
This method is preferred by fitness professionals because it incorporates your Resting Heart Rate (RHR), making the zones more accurate to your specific fitness level.
Example: For a 40-year-old with a resting heart rate of 60 bpm:
MHR = 180.
HRR = 180 – 60 = 120.
Calculation = (120 × 0.50) + 60 = 60 + 60 = 120 bpm.
Notice that the Karvonen formula suggests a higher minimum target (120 bpm vs 90 bpm) because it accounts for the individual's baseline cardiovascular efficiency.
Target Heart Rate Zones Explained
Once you know your minimum, you can explore the different zones:
Zone 1 (50-60%): Very Light. Best for warm-ups, cool-downs, and recovery. This is your minimum target floor.
Zone 2 (60-70%): Light to Moderate. Ideally suited for long-duration endurance training and fat oxidation. You should be able to hold a conversation easily.
Zone 3 (70-80%): Moderate to Vigorous. Improves aerobic capacity and blood circulation. Conversation becomes difficult.
Zone 4 (80-90%): Hard. Increases maximum performance capacity. Sustainable for shorter periods only.
How to Measure Your Heart Rate
To ensure you are hitting your calculated minimum target, you can use a wearable fitness tracker, a chest strap monitor, or measure it manually. To measure manually, place your index and middle fingers on your radial artery (wrist) or carotid artery (neck), count the beats for 10 seconds, and multiply by 6.