Heart Rate Zone 2 Calculation Formula

Zone 2 Heart Rate Calculator

Your Results

Your Max Heart Rate (Estimated): 0 BPM

Zone 2 Target Range:

0 – 0 BPM

(Based on Karvonen Formula: 60% – 70% Heart Rate Reserve)

function calculateZone2() { var age = parseFloat(document.getElementById('age').value); var rhr = parseFloat(document.getElementById('rhr').value); var resultArea = document.getElementById('results-area'); if (isNaN(age) || age 110) { alert("Please enter a valid age."); return; } if (isNaN(rhr) || rhr 120) { alert("Please enter a valid resting heart rate (typical 30-120)."); return; } // Using the Tanaka formula for more accuracy: 208 – (0.7 * age) var mhr = Math.round(208 – (0.7 * age)); // Karvonen Formula calculation // Target HR = ((MHR – RHR) * %Intensity) + RHR var hrr = mhr – rhr; var z2low = Math.round((hrr * 0.60) + rhr); var z2high = Math.round((hrr * 0.70) + rhr); document.getElementById('mhr-display').innerHTML = mhr; document.getElementById('zone2-range').innerHTML = z2low + " – " + z2high + " BPM"; resultArea.style.display = 'block'; }

Understanding the Heart Rate Zone 2 Calculation

Zone 2 training has become the cornerstone of endurance athletics and longevity protocols. Often referred to as "base training" or "aerobic threshold training," Zone 2 is the intensity level where your body optimizes its ability to burn fat as a primary fuel source while increasing mitochondrial density and efficiency.

The Karvonen Formula vs. Age-Based Calculation

Many basic calculators simply use 220 minus age. However, this method is often inaccurate because it ignores your Resting Heart Rate (RHR). Our calculator utilizes the Karvonen Formula, which calculates your Heart Rate Reserve (HRR) to provide a personalized intensity range.

The formula works as follows:

• Max HR: 208 – (0.7 × Age)
• Heart Rate Reserve (HRR): Max HR – Resting HR
• Zone 2 Low (60%): (HRR × 0.60) + Resting HR
• Zone 2 High (70%): (HRR × 0.70) + Resting HR

Why Is Zone 2 Important?

Training in Zone 2 triggers specific physiological adaptations that higher intensity "no-man's land" training (Zone 3) does not. These benefits include:

1. Mitochondrial Health: It increases the number and efficiency of mitochondria in your slow-twitch muscle fibers.
2. Lactate Clearance: It improves your body's ability to clear lactate, allowing you to sustain higher intensities for longer periods.
3. Fat Oxidation: It teaches the body to utilize fatty acids more effectively, preserving glycogen for high-intensity efforts.

Practical Examples

Example 1: A 40-year-old athlete with a resting heart rate of 60 BPM.
Estimated Max HR: 180 BPM.
Heart Rate Reserve: 120 BPM.
Zone 2 Range: 132 – 144 BPM.

Example 2: A 25-year-old beginner with a resting heart rate of 75 BPM.
Estimated Max HR: 191 BPM.
Heart Rate Reserve: 116 BPM.
Zone 2 Range: 145 – 156 BPM.

The "Talk Test"

If you don't have a heart rate monitor, you can use the subjective "Talk Test." In Zone 2, you should be able to hold a full conversation without gasping for air, but your breathing should be noticeably deeper than when you are at rest. If you can only speak in short sentences, you have likely crossed into Zone 3.