How to Find My Zone 2 Heart Rate Calculator

Zone 2 Heart Rate Calculator

Measure this first thing in the morning for best accuracy.

Your Zone 2 Training Range

BPM

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

Max Heart Rate (Est.): BPM

Heart Rate Reserve: BPM

Please enter valid numbers for age and resting heart rate.

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What is Zone 2 Heart Rate Training?

Zone 2 training is often referred to as "aerobic base training." It is a steady-state intensity where your body primarily uses fat as a fuel source through aerobic metabolism. This specific intensity level is sustainable for long periods and is a cornerstone for endurance athletes and those looking to improve metabolic health.

How This Calculator Works

While many simple calculators just take a percentage of your Max Heart Rate (220 – Age), this calculator uses the Karvonen Formula. This method is more accurate because it accounts for your Resting Heart Rate (RHR), which reflects your current fitness level.

The math behind it:

• Max HR: 220 – 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

Example Calculation

If you are 40 years old with a resting heart rate of 65 BPM:

1. Estimated Max HR: 220 – 40 = 180 BPM
2. Heart Rate Reserve: 180 – 65 = 115 BPM
3. 60% intensity: (115 × 0.60) + 65 = 134 BPM
4. 70% intensity: (115 × 0.70) + 65 = 145 BPM
5. Zone 2 Range: 134 – 145 BPM

Why Train in Zone 2?

Training at this intensity triggers physiological adaptations that higher-intensity workouts cannot. These include:

• Mitochondrial Density: Increases the number and efficiency of mitochondria in your muscle cells.
• Fat Oxidation: Improves your body's ability to burn fat as fuel rather than relying solely on glycogen (carbohydrates).
• Capillary Density: Improves blood flow and oxygen delivery to your muscles.
• Recovery: Zone 2 sessions are low-stress, meaning you can perform them frequently without overtraining.

How to Verify You Are in Zone 2

Beyond the numbers on your heart rate monitor, you can use the "Talk Test." In Zone 2, you should be able to carry on a full conversation without gasping for air, though you should sound like you are exercising. If you can only speak in short sentences, you have likely drifted into Zone 3.

function calculateZone2() { var age = parseFloat(document.getElementById("userAge").value); var rhr = parseFloat(document.getElementById("restingHR").value); var resultsArea = document.getElementById("resultsArea"); var errorArea = document.getElementById("errorArea"); if (isNaN(age) || isNaN(rhr) || age <= 0 || rhr 110) { resultsArea.style.display = "none"; errorArea.style.display = "block"; return; } errorArea.style.display = "none"; var maxHR = 220 – age; var hrr = maxHR – rhr; if (hrr <= 0) { resultsArea.style.display = "none"; errorArea.innerText = "Resting heart rate cannot be higher than maximum heart rate."; errorArea.style.display = "block"; return; } var lowLimit = Math.round((hrr * 0.60) + rhr); var highLimit = Math.round((hrr * 0.70) + rhr); document.getElementById("rangeOutput").innerText = lowLimit + " – " + highLimit; document.getElementById("maxHROutput").innerText = maxHR; document.getElementById("hrrOutput").innerText = hrr; resultsArea.style.display = "block"; resultsArea.scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }