Zone 2 Heart Rate Calculation Formula

Zone 2 Heart Rate Calculator

Karvonen Formula (Most Accurate – Requires Resting HR) Percentage of Max HR (Simple Method)

Your Zone 2 Training Range:

0 – 0 BPM

Please enter a valid age and resting heart rate.

function calculateZone2() { var age = parseFloat(document.getElementById('userAge').value); var rhr = parseFloat(document.getElementById('userRHR').value); var method = document.getElementById('calcMethod').value; var resultsArea = document.getElementById('resultsArea'); var errorArea = document.getElementById('errorArea'); if (isNaN(age) || age 110) { errorArea.style.display = 'block'; resultsArea.style.display = 'none'; return; } if (method === 'karvonen' && (isNaN(rhr) || rhr 120)) { errorArea.style.display = 'block'; resultsArea.style.display = 'none'; return; } errorArea.style.display = 'none'; var maxHR = 220 – age; var lowBPM, highBPM, note; if (method === 'karvonen') { // Heart Rate Reserve (HRR) = Max HR – Resting HR // Zone 2 is typically 60% to 70% of HRR + RHR var hrr = maxHR – rhr; lowBPM = Math.round((hrr * 0.60) + rhr); highBPM = Math.round((hrr * 0.70) + rhr); note = "Calculated using the Karvonen Formula (60-70% of Heart Rate Reserve)."; } else { // Simple percentage of Max HR // Zone 2 is typically 60% to 70% of Max HR lowBPM = Math.round(maxHR * 0.60); highBPM = Math.round(maxHR * 0.70); note = "Calculated as 60-70% of your predicted Maximum Heart Rate (" + maxHR + " BPM)."; } document.getElementById('lowBound').innerText = lowBPM; document.getElementById('highBound').innerText = highBPM; document.getElementById('methodNote').innerText = note; resultsArea.style.display = 'block'; }

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Understanding the Zone 2 Heart Rate Calculation Formula

Zone 2 training is often called "base training" or "aerobic capacity training." It is the intensity at which your body primarily uses fat as fuel and builds mitochondrial density. To reap the benefits, you must stay within a specific heart rate range.

Method 1: The Karvonen Formula

The Karvonen formula is considered more accurate than simple percentages because it takes your Resting Heart Rate (RHR) into account. This accounts for individual fitness levels (a lower RHR usually indicates higher cardiovascular efficiency).

Formula: ((Max HR − Resting HR) × %Intensity) + Resting HR
Example for a 40-year-old with a 60 RHR:
Max HR = 180 (220-40)
HR Reserve = 120 (180-60)
Lower Bound (60%) = (120 * 0.6) + 60 = 132 BPM

Method 2: Percentage of Maximum Heart Rate

This is the standard formula used by many commercial gym machines and basic fitness trackers. It simply takes your age-predicted maximum heart rate (220 – age) and calculates 60% to 70% of that number.

• Pros: Extremely easy to calculate.
• Cons: Can be inaccurate for highly trained athletes or those with naturally high/low maximum heart rates.

Why Train in Zone 2?

Training in Zone 2 is the "sweet spot" for metabolic health. Unlike high-intensity intervals (HIIT), Zone 2 training:

• Increases the number and efficiency of mitochondria.
• Improves lactate clearance capacity.
• Builds a massive aerobic engine for endurance sports.
• Reduces the risk of overtraining and injury.

The "Talk Test" Check

A great way to verify your Zone 2 calculation is the "Talk Test." If you are in Zone 2, you should be able to maintain a full conversation without gasping for air, but you should sound like you are exercising. If you can only speak in short sentences, you have likely drifted into Zone 3.