Formula Comparison:
(Traditional Fox)
(Gulati – Female Specific)
What is Maximum Predicted Heart Rate?
Your Maximum Heart Rate (MHR or HRmax) is the highest number of times your heart can beat in one minute under maximum physical stress. It is a crucial metric for athletes, fitness enthusiasts, and medical professionals to determine safe exercise limits and optimal training intensities.
Unlike resting heart rate, which can change significantly with fitness levels, your MHR is largely determined by your age and genetics. It naturally decreases as you get older. Knowing your MHR allows you to train in specific "zones" to target fat loss, endurance, or anaerobic capacity.
How the Calculator Works
This calculator utilizes multiple scientific formulas to provide the most accurate prediction possible. While the "220 minus age" rule is famous, modern science has provided more precise equations.
1. The Tanaka Formula (Primary)
Formula: 208 – (0.7 × Age)
Considered the gold standard for healthy adults, the Tanaka equation was developed to correct the inaccuracies of older formulas found in different age groups.
2. The Fox Formula (Traditional)
Formula: 220 – Age
This is the simplest and most widely known method. While easy to calculate mentally, it tends to overestimate MHR for younger people and underestimate it for older adults.
3. The Gulati Formula (For Women)
Formula: 206 – (0.88 × Age)
Research indicates that the standard formulas often overestimate MHR in women. The Gulati formula is specifically calibrated to provide a more accurate maximum heart rate prediction for females.
Understanding Heart Rate Training Zones
Once you know your MHR, you can structure your exercise based on percentage zones. If you entered your Resting Heart Rate (RHR), this calculator uses the Karvonen Method, which accounts for your fitness level (Heart Rate Reserve). If no RHR was entered, it uses standard percentages of MHR.
Zone 1 (50-60%): Warm Up / Recovery. Good for beginners and warming up. Improves overall health and helps recovery.
Zone 2 (60-70%): Fat Burning. The "sweet spot" for metabolism. The body becomes efficient at using fat as fuel.
Zone 3 (70-80%): Aerobic Endurance. Improves blood circulation and skeletal muscle strength. This is where cardiovascular fitness is built.
Zone 4 (80-90%): Anaerobic / Hard. Increases performance speed and lactate tolerance. Difficult to sustain for long periods.
Zone 5 (90-100%): Maximum Effort. For short bursts only. Improves speed and power but carries higher risk if not trained properly.
Safety Disclaimer
This calculator provides an estimate based on population averages. Your actual maximum heart rate can vary by 10-20 beats per minute due to genetics, medication, and specific medical conditions. Always consult a physician before starting a new exercise program, especially if you have a history of heart conditions.
function calculateHeartRate() {
// 1. Get Inputs
var ageInput = document.getElementById('hr_age');
var genderSelect = document.getElementById('hr_gender');
var restingInput = document.getElementById('hr_resting');
var age = parseFloat(ageInput.value);
var gender = genderSelect.value;
var restingHR = parseFloat(restingInput.value);
// 2. Validate Age
if (isNaN(age) || age 120) {
alert("Please enter a valid age between 1 and 120.");
return;
}
// 3. Calculate Different Formulas
// Fox Formula (Standard)
var foxMHR = 220 – age;
// Tanaka Formula (Generally more accurate for adults)
var tanakaMHR = 208 – (0.7 * age);
// Gulati Formula (Specific for women)
var gulatiMHR = 206 – (0.88 * age);
// Determine Primary Result based on context
// We will use Tanaka as the main display as it's generally best for mixed populations
// But if female, Gulati is scientifically preferred.
var primaryMHR = Math.round(tanakaMHR);
// If female, we might favor Gulati, but Tanaka is still very standard.
// Let's stick to Tanaka for the big number for consistency, but reference Gulati below if female.
if (gender === 'female') {
// Option: Swap primary to Gulati for females?
// Let's keep Tanaka as primary but show Gulati clearly.
// Actually, for a specialized calculator, adapting to Gulati for women is smarter logic.
primaryMHR = Math.round(gulatiMHR);
}
// 4. Calculate Zones
// If Resting HR is provided, use Karvonen Formula:
// TargetHR = ((MaxHR – RestingHR) * %Intensity) + RestingHR
var useKarvonen = !isNaN(restingHR) && restingHR > 30 && restingHR < 200;
// Zone Percentages
var zones = [
{ name: "Zone 1 (Warm Up)", minPct: 0.50, maxPct: 0.60, desc: "Recovery & Health" },
{ name: "Zone 2 (Fat Burn)", minPct: 0.60, maxPct: 0.70, desc: "Weight Management" },
{ name: "Zone 3 (Aerobic)", minPct: 0.70, maxPct: 0.80, desc: "Cardio Fitness" },
{ name: "Zone 4 (Anaerobic)", minPct: 0.80, maxPct: 0.90, desc: "Performance Training" },
{ name: "Zone 5 (Maximum)", minPct: 0.90, maxPct: 1.00, desc: "Speed & Power" }
];
var zonesHtml = "";
for (var i = 0; i < zones.length; i++) {
var minBPM, maxBPM;
if (useKarvonen) {
// Karvonen Calculation
// Heart Rate Reserve = PrimaryMHR – RestingHR
var hrr = primaryMHR – restingHR;
minBPM = Math.round((hrr * zones[i].minPct) + restingHR);
maxBPM = Math.round((hrr * zones[i].maxPct) + restingHR);
} else {
// Standard Percentage Calculation
minBPM = Math.round(primaryMHR * zones[i].minPct);
maxBPM = Math.round(primaryMHR * zones[i].maxPct);
}
zonesHtml += "
";
zonesHtml += "
" + zones[i].name + "
";
zonesHtml += "
" + minBPM + " – " + maxBPM + " bpm
";
zonesHtml += "
" + zones[i].desc + "
";
zonesHtml += "
";
}
// 5. Update DOM
document.getElementById('hr_main_display').innerText = primaryMHR + " BPM";
// Formula comparison text
document.getElementById('hr_fox_result').innerText = "Fox Formula (220-Age): " + Math.round(foxMHR) + " bpm";
var gulatiText = "Gulati Formula: " + Math.round(gulatiMHR) + " bpm";
if (gender === 'female') {
gulatiText = "" + gulatiText + " (Recommended for Women)";
}
document.getElementById('hr_gulati_result').innerHTML = gulatiText;
// Subtitle update
var formulaName = (gender === 'female') ? "Gulati Formula" : "Tanaka Formula";
document.querySelector('.hr-subtitle').innerHTML = "Based on " + formulaName + (useKarvonen ? " & Karvonen Method" : "");
document.getElementById('hr_zones_body').innerHTML = zonesHtml;
// Show results
document.getElementById('hr_result_container').style.display = "block";
// Scroll to results
document.getElementById('hr_result_container').scrollIntoView({ behavior: 'smooth' });
}