*BPM = Beats Per Minute. These figures are estimates based on population averages.
function calculateHeartRate() {
// Get Inputs
var age = parseFloat(document.getElementById('inputAge').value);
var formula = document.getElementById('inputFormula').value;
var resultContainer = document.getElementById('resultContainer');
var mhrDisplay = document.getElementById('mhrDisplay');
var tableBody = document.getElementById('zonesTableBody');
// Validation
if (isNaN(age) || age 120) {
alert("Please enter a valid age between 1 and 120.");
resultContainer.style.display = "none";
return;
}
// MHR Calculation Logic
var mhr = 0;
if (formula === 'standard') {
// Fox Formula: 220 – age
mhr = 220 – age;
} else if (formula === 'tanaka') {
// Tanaka: 208 – (0.7 * age)
mhr = 208 – (0.7 * age);
} else if (formula === 'gulati') {
// Gulati (Women): 206 – (0.88 * age)
mhr = 206 – (0.88 * age);
} else if (formula === 'gellish') {
// Gellish: 207 – (0.7 * age)
mhr = 207 – (0.7 * age);
}
// Round MHR to nearest whole number
mhr = Math.round(mhr);
// Update Main Display
resultContainer.style.display = "block";
mhrDisplay.innerHTML = mhr + " BPM";
// Calculate Zones
// Zone 1: 50-60% Very Light
// Zone 2: 60-70% Light
// Zone 3: 70-80% Moderate
// Zone 4: 80-90% Hard
// Zone 5: 90-100% Maximum
var z1_low = Math.round(mhr * 0.50);
var z1_high = Math.round(mhr * 0.60);
var z2_low = Math.round(mhr * 0.60);
var z2_high = Math.round(mhr * 0.70);
var z3_low = Math.round(mhr * 0.70);
var z3_high = Math.round(mhr * 0.80);
var z4_low = Math.round(mhr * 0.80);
var z4_high = Math.round(mhr * 0.90);
var z5_low = Math.round(mhr * 0.90);
var z5_high = mhr;
// Generate Table HTML
var html = ";
// Zone 5
html += '
';
html += '
Zone 5
';
html += '
Maximum (90-100%)
';
html += '
' + z5_low + ' – ' + z5_high + '
';
html += '
Speed & Power, Short Bursts
';
html += '
';
// Zone 4
html += '
';
html += '
Zone 4
';
html += '
Hard (80-90%)
';
html += '
' + z4_low + ' – ' + z4_high + '
';
html += '
Anaerobic Capacity, Endurance
';
html += '
';
// Zone 3
html += '
';
html += '
Zone 3
';
html += '
Moderate (70-80%)
';
html += '
' + z3_low + ' – ' + z3_high + '
';
html += '
Aerobic Fitness, Blood Circulation
';
html += '
';
// Zone 2
html += '
';
html += '
Zone 2
';
html += '
Light (60-70%)
';
html += '
' + z2_low + ' – ' + z2_high + '
';
html += '
Fat Burning, Basic Endurance
';
html += '
';
// Zone 1
html += '
';
html += '
Zone 1
';
html += '
Very Light (50-60%)
';
html += '
' + z1_low + ' – ' + z1_high + '
';
html += '
Warm up, Recovery
';
html += '
';
tableBody.innerHTML = html;
}
Understanding Maximum Heart Rate (MHR) by Age
Your Maximum Heart Rate (MHR) is the highest number of beats per minute (BPM) your heart can pump under maximum stress. Calculating this number is a foundational step in designing an effective exercise program, as it helps define your personal heart rate training zones.
Common Calculation Formulas
While a clinical stress test is the most accurate way to measure MHR, several mathematical formulas provide reasonable estimates based on age:
The "Fox" Formula (Standard):220 - Age. This is the most widely used and simplest formula, though it tends to overestimate MHR in younger people and underestimate it in older adults.
The Tanaka Formula:208 - (0.7 × Age). Developed in 2001, this formula is generally considered more accurate for healthy adults over age 40.
The Gulati Formula:206 - (0.88 × Age). Research suggests the standard formula often overestimates MHR for women. The Gulati formula is specifically adjusted for female physiology.
Why Do Heart Rate Zones Matter?
Training at different percentages of your MHR triggers different physiological adaptations. Instead of just "exercising," utilizing zones allows you to target specific goals:
Zone 2: The Fat Burning Zone (60-70% MHR)
In this zone, the body relies heavily on fat as a fuel source. It is conversational, meaning you should be able to speak in full sentences while training. It builds your aerobic base and endurance without placing high stress on the body.
Example: A 40-year-old using the standard formula (MHR 180) would target 108 to 126 BPM.
Zone 3: The Aerobic Zone (70-80% MHR)
This is the "sweet spot" for improving cardiovascular health. Training here improves your heart's ability to pump blood and your muscles' ability to utilize oxygen. Breathing becomes heavier, but you can still speak in short phrases.
Zone 4 & 5: Anaerobic and Peak (80-100% MHR)
These high-intensity zones are used for interval training (HIIT) to improve speed, power, and lactate threshold. Efforts here are sustainable only for short periods due to the buildup of lactic acid.
Safety and Limitations
Please note that these calculations are statistical averages. Your actual maximum heart rate can vary based on genetics, fitness history, and medications (such as beta-blockers, which lower heart rate). Always consult a healthcare professional before beginning a vigorous new exercise regimen, especially if you have a history of cardiovascular issues.