How to Calculate Heart Rate for Cardio

Target Heart Rate Calculator

Your Personal Heart Rate Data:

Estimated Max Heart Rate: BPM

Heart Rate Reserve (HRR): BPM

Intensity Zone Target BPM Range
Moderate (50% – 70%)
Vigorous (70% – 85%)
Aerobic Capacity (85%+)

How to Calculate Heart Rate for Cardio Success

Understanding your heart rate is the most effective way to gauge the intensity of your workouts. Whether you are training for a marathon or trying to lose weight, monitoring your beats per minute (BPM) ensures you are pushing hard enough to see results without overtraining.

The Karvonen Formula Explained

This calculator uses the Karvonen Formula, which is considered more accurate than the simple "220 minus age" method because it accounts for your unique fitness level by including your Resting Heart Rate (RHR).

The formula follows these steps:

  • Max Heart Rate (MHR): 220 – Age
  • Heart Rate Reserve (HRR): MHR – Resting Heart Rate
  • Target Heart Rate: (HRR × % Intensity) + Resting Heart Rate

Training Zones and Their Benefits

Moderate Intensity (50% – 70%): Often called the "Fat Burning Zone." Ideal for long-duration activities, warm-ups, and recovery. It builds endurance and improves metabolic efficiency.

Vigorous Intensity (70% – 85%): The "Cardio Zone." This improves cardiovascular fitness, increases lung capacity, and strengthens the heart muscle. This is where most aerobic conditioning occurs.

Peak Intensity (85%+): The "Performance Zone." Used for high-intensity interval training (HIIT) and sprints. It improves speed and anaerobic threshold but should be used sparingly.

Realistic Example Calculation

User Profile: 40 years old with a Resting Heart Rate of 60 BPM.

  • Max Heart Rate: 220 – 40 = 180 BPM
  • Heart Rate Reserve: 180 – 60 = 120 BPM
  • 70% Intensity: (120 × 0.70) + 60 = 144 BPM
  • Target for Vigorous Activity: 144 to 162 BPM

Tips for Accurate Measurements

To find your true Resting Heart Rate, measure your pulse for 60 seconds immediately after waking up, before you get out of bed. Doing this over three consecutive mornings and taking the average provides the most reliable data for your cardio calculations.

function calculateCardioZones() { var age = parseFloat(document.getElementById("userAge").value); var rhr = parseFloat(document.getElementById("restingHR").value); var resultsDiv = document.getElementById("hr-results"); if (isNaN(age) || age 120) { alert("Please enter a valid age."); return; } if (isNaN(rhr) || rhr 150) { alert("Please enter a valid resting heart rate (typical range is 40-100 BPM)."); return; } var mhr = 220 – age; var hrr = mhr – rhr; if (hrr <= 0) { alert("Resting heart rate cannot be higher than your max heart rate. Please check your inputs."); return; } // Moderate Intensity: 50% – 70% var modLow = Math.round((hrr * 0.50) + rhr); var modHigh = Math.round((hrr * 0.70) + rhr); // Vigorous Intensity: 70% – 85% var vigLow = Math.round((hrr * 0.70) + rhr); var vigHigh = Math.round((hrr * 0.85) + rhr); // Peak Intensity: 85% – 95% var peakLow = Math.round((hrr * 0.85) + rhr); var peakHigh = Math.round((hrr * 0.95) + rhr); // Update UI document.getElementById("maxResult").innerText = mhr; document.getElementById("hrrResult").innerText = hrr; document.getElementById("moderateZone").innerText = modLow + " – " + modHigh + " BPM"; document.getElementById("vigorousZone").innerText = vigLow + " – " + vigHigh + " BPM"; document.getElementById("peakZone").innerText = peakLow + " – " + peakHigh + " BPM"; resultsDiv.style.display = "block"; }

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