Heart Rate Reserve is Used to Calculate

Heart Rate Reserve (Karvonen) Calculator

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Max Heart Rate (Estimated) —

Heart Rate Reserve (HRR) —

Target Heart Rate for Chosen Intensity — Beats Per Minute

What is Heart Rate Reserve (HRR)?

Heart Rate Reserve (HRR) is the difference between your measured or predicted maximum heart rate and your resting heart rate. It represents the cushion of heart beats you have available for physical activity. The HRR method is widely considered more accurate than the simple age-based formula because it accounts for an individual's cardiovascular fitness level via the resting heart rate.

The Karvonen Formula

The calculation performed by this tool uses the Karvonen Formula, which is the gold standard for determining exercise intensity for athletes and fitness enthusiasts. The formula is expressed as:

Target Heart Rate = [(Max HR − Resting HR) × % Intensity] + Resting HR

Why Heart Rate Reserve is Used to Calculate Intensity

Heart Rate Reserve is used to calculate target heart rate zones because it mirrors the percentage of oxygen consumption (VO2 Max) more closely than just using a percentage of Maximum Heart Rate alone. By including your resting heart rate in the equation, the formula adjusts for your baseline fitness. For example, an elite athlete with a resting heart rate of 40 bpm will have a much larger HRR than a sedentary person with a resting heart rate of 80 bpm, even if they are the same age.

Common Intensity Zones

• Moderate Intensity (50% – 70%): Ideal for long-duration endurance training and fat metabolism.
• Vigorous Intensity (70% – 85%): Enhances aerobic capacity and improves cardiovascular health.
• Competitive Intensity (85% – 95%): Increases anaerobic threshold and top-end speed/power.

Example Calculation

Suppose a 40-year-old individual has a resting heart rate of 60 bpm and wants to exercise at 75% intensity:

1. Max HR: 220 – 40 = 180 bpm
2. Heart Rate Reserve (HRR): 180 – 60 = 120 bpm
3. Target HR: (120 × 0.75) + 60 = 150 bpm

function calculateHRR() { var age = parseFloat(document.getElementById("userAge").value); var restingHR = parseFloat(document.getElementById("restingHR").value); var intensity = parseFloat(document.getElementById("intensity").value) / 100; if (isNaN(age) || isNaN(restingHR) || age <= 0 || restingHR <= 0) { alert("Please enter valid numbers for age and resting heart rate."); return; } // Standard Max HR estimation: 220 – age var maxHR = 220 – age; // Heart Rate Reserve Calculation var hrr = maxHR – restingHR; if (hrr <= 0) { alert("Resting heart rate cannot be higher than maximum heart rate. Please check your inputs."); return; } // Karvonen Formula: THR = (HRR * intensity) + restingHR var targetHR = (hrr * intensity) + restingHR; // Update UI document.getElementById("maxHRVal").innerHTML = Math.round(maxHR) + " bpm"; document.getElementById("hrrVal").innerHTML = Math.round(hrr) + " bpm"; document.getElementById("targetHRVal").innerHTML = Math.round(targetHR); document.getElementById("hrr-results").style.display = "block"; // Scroll results into view document.getElementById("hrr-results").scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }