Jack Daniels Heart Rate Zones Calculator

Jack Daniels Heart Rate Zones Calculator

If unknown, use 220 minus your age.
Used for Karvonen formula (Heart Rate Reserve).

Your Training Intensity Zones

Zone Intensity (%) HR Range (BPM)

*Calculated using the Karvonen formula: [(HRmax – HRrest) × %Intensity] + HRrest.


Understanding Jack Daniels Training Zones

Dr. Jack Daniels, named the "World's Best Running Coach" by Runner's World, developed the VDOT system to help runners train at the precise intensities needed to improve physiological systems. While VDOT is primarily pace-based, heart rate serves as a critical biological feedback tool to ensure you aren't overtraining or undertraining.

The Five Primary Intensity Zones

  • Easy (E) Pace (65-79% HRmax): Used for warm-ups, cool-downs, and long runs. This builds aerobic capacity and strengthens tendons and ligaments without excessive fatigue.
  • Marathon (M) Pace (80-90% HRmax): A steady-state intensity specific to marathon racing. It is faster than Easy pace but slower than Threshold.
  • Threshold (T) Pace (88-92% HRmax): Also known as "tempo" running. This is the intensity that improves your lactate threshold, allowing you to maintain a faster pace for a longer duration.
  • Interval (I) Pace (95-100% HRmax): Aimed at increasing VO2 Max (aerobic power). These are usually 3-5 minute hard efforts with recovery periods.
  • Repetition (R) Pace: Not typically monitored by heart rate because the efforts are too short (30-90 seconds) for HR to stabilize. These focus on speed and running economy.

Why Use the Karvonen Formula?

This calculator uses the Heart Rate Reserve (HRR) method. Unlike a simple percentage of maximum heart rate, HRR accounts for your resting heart rate. This is more accurate for trained athletes because it reflects your actual aerobic range—the difference between your heart at total rest and your heart at maximum effort.

Example Calculation

If an athlete has a Max HR of 190 and a Resting HR of 50, their Heart Rate Reserve is 140. To find the lower end of the "Threshold" zone (88%):

(140 × 0.88) + 50 = 173 BPM.

function calculateDanielsZones() { var maxHR = parseFloat(document.getElementById('maxHR').value); var restHR = parseFloat(document.getElementById('restHR').value); var resultsArea = document.getElementById('resultsArea'); var tableBody = document.getElementById('zoneTableBody'); if (!maxHR || !restHR || maxHR <= restHR) { alert("Please enter valid Heart Rate values. Max HR must be higher than Resting HR."); return; } var hrr = maxHR – restHR; var zones = [ { name: "Easy (E)", min: 0.65, max: 0.79, desc: "Recovery and Aerobic Base" }, { name: "Marathon (M)", min: 0.80, max: 0.90, desc: "Specific Endurance" }, { name: "Threshold (T)", min: 0.88, max: 0.92, desc: "Lactate Threshold Improvement" }, { name: "Interval (I)", min: 0.95, max: 1.00, desc: "VO2 Max Development" } ]; tableBody.innerHTML = ""; for (var i = 0; i < zones.length; i++) { var zone = zones[i]; var lowBPM = Math.round((hrr * zone.min) + restHR); var highBPM = Math.round((hrr * zone.max) + restHR); var row = document.createElement('tr'); row.style.borderBottom = "1px solid #eee"; var cellName = document.createElement('td'); cellName.style.padding = "12px"; cellName.innerHTML = "" + zone.name + "" + zone.desc + ""; var cellPerc = document.createElement('td'); cellPerc.style.padding = "12px"; cellPerc.innerText = (zone.min * 100) + "% – " + (zone.max * 100) + "%"; var cellRange = document.createElement('td'); cellRange.style.padding = "12px"; cellRange.style.fontWeight = "bold"; cellRange.style.color = "#d32f2f"; cellRange.innerText = lowBPM + " – " + highBPM + " BPM"; row.appendChild(cellName); row.appendChild(cellPerc); row.appendChild(cellRange); tableBody.appendChild(row); } resultsArea.style.display = "block"; resultsArea.scrollIntoView({ behavior: 'smooth' }); }

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