Heart Rate Zone Pace Calculator

Used to estimate Max Heart Rate if unknown.

Best measured upon waking up.

Your Personalized Training Zones

Zone	Intensity	Heart Rate (BPM)	Target Pace (/km)

*Paces are estimates based on your 5k performance. Heart Rate ranges calculated using the Karvonen Formula (Heart Rate Reserve).

function calculateHRZones() { var age = parseFloat(document.getElementById('hrAge').value); var rhr = parseFloat(document.getElementById('hrResting').value); var min5k = parseFloat(document.getElementById('hr5kMin').value); var sec5k = parseFloat(document.getElementById('hr5kSec').value); if (isNaN(age) || isNaN(rhr) || isNaN(min5k)) { alert('Please enter valid numbers'); return; } var mhr = 220 – age; var hrr = mhr – rhr; var total5kSeconds = (min5k * 60) + sec5k; var basePacePerKm = total5kSeconds / 5; // Seconds per KM var zones = [ { name: "Zone 1 (Recovery)", lowHR: 0.50, highHR: 0.60, paceMultLow: 1.45, paceMultHigh: 1.60, desc: "Very Easy/Warmup" }, { name: "Zone 2 (Aerobic)", lowHR: 0.60, highHR: 0.70, paceMultLow: 1.25, paceMultHigh: 1.45, desc: "Endurance/Base" }, { name: "Zone 3 (Tempo)", lowHR: 0.70, highHR: 0.80, paceMultLow: 1.05, paceMultHigh: 1.15, desc: "Steady/Marathon" }, { name: "Zone 4 (Threshold)", lowHR: 0.80, highHR: 0.90, paceMultLow: 0.98, paceMultHigh: 1.05, desc: "Hard/10k Pace" }, { name: "Zone 5 (Anaerobic)", lowHR: 0.90, highHR: 1.00, paceMultLow: 0.85, paceMultHigh: 0.95, desc: "Max Effort/Sprint" } ]; var html = ""; for (var i = 0; i < zones.length; i++) { var z = zones[i]; var hrLow = Math.round((hrr * z.lowHR) + rhr); var hrHigh = Math.round((hrr * z.highHR) + rhr); var paceSecLow = basePacePerKm * z.paceMultLow; var paceSecHigh = basePacePerKm * z.paceMultHigh; function formatPace(s) { var m = Math.floor(s / 60); var sec = Math.round(s % 60); return m + ":" + (sec < 10 ? "0" + sec : sec); } html += ""; html += "" + z.name + ""; html += "" + z.desc + ""; html += "" + hrLow + " – " + hrHigh + ""; html += "" + formatPace(paceSecHigh) + " – " + formatPace(paceSecLow) + ""; html += ""; } document.getElementById('hrTableBody').innerHTML = html; document.getElementById('hrResults').style.display = 'block'; }

How to Use the Heart Rate Zone Pace Calculator

Optimizing your running performance requires training at the correct intensity. This calculator uses two primary data points to build your training profile: the Karvonen Formula for heart rate zones and your 5k race pace for velocity targets.

The Importance of Heart Rate Zones

Training zones allow you to target specific physiological adaptations. By knowing your heart rate ranges, you can ensure your "easy" runs are truly easy enough to facilitate recovery, and your "hard" runs are intense enough to improve your VO2 max.

• Zone 2 (60-70% HRR): This is the "sweet spot" for building aerobic capacity and mitochondrial density. Most of your weekly mileage should be here.
• Zone 4 (80-90% HRR): Often called the Lactate Threshold zone. This improves your body's ability to clear lactic acid and sustain faster speeds for longer.

Calculating Your Maximum Heart Rate

While this calculator uses the standard 220-Age formula for convenience, athletes with a known Max HR (tested during a hill sprint or lab test) can adjust their age input to match their known peak. The Resting Heart Rate is equally critical; measuring it first thing in the morning ensures the Heart Rate Reserve (HRR) calculation is accurate.

Practical Example

If you are 40 years old with a resting heart rate of 60 bpm and a 5k personal best of 25:00:

1. Max HR: 180 bpm
2. HR Reserve: 120 bpm
3. Zone 2 Target: 132 – 144 bpm
4. Zone 2 Pace: Approximately 6:15 – 7:15 per kilometer

By matching your heart rate to these pace ranges, you can adjust your effort based on weather, terrain, and daily fatigue, ensuring you never overtrain or underperform.