Interval Training Heart Rate Calculator

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Interval Training Heart Rate Calculator

Your Training Targets:

Estimated Max HR – BPM
Heart Rate Reserve (HRR) – BPM
Work Interval Target (High Intensity) – BPM
Recovery Interval Target (Low Intensity) – BPM
function calculateIntervalHR() { var age = parseFloat(document.getElementById('hrAge').value); var restHR = parseFloat(document.getElementById('hrRest').value); var highPct = parseFloat(document.getElementById('hrHighPct').value) / 100; var lowPct = parseFloat(document.getElementById('hrLowPct').value) / 100; if (isNaN(age) || isNaN(restHR) || isNaN(highPct) || isNaN(lowPct)) { alert("Please enter valid numerical values."); return; } // Karvonen Formula // Max HR estimation (Haskell & Fox) var maxHR = 220 – age; // Heart Rate Reserve (HRR) var hrr = maxHR – restHR; // Target HR = (HRR * intensity) + restHR var workHR = (hrr * highPct) + restHR; var recoveryHR = (hrr * lowPct) + restHR; document.getElementById('resMaxHR').innerText = Math.round(maxHR); document.getElementById('resHRR').innerText = Math.round(hrr); document.getElementById('resWorkHR').innerText = Math.round(workHR); document.getElementById('resRecHR').innerText = Math.round(recoveryHR); document.getElementById('hrResults').style.display = 'block'; }

How to Use the Interval Training Heart Rate Calculator

High-Intensity Interval Training (HIIT) and specialized cardiovascular work require precision. Unlike steady-state cardio, interval training relies on alternating between periods of intense work and active recovery. To maximize the physiological benefits—such as increased VO2 max and metabolic rate—you must hit specific heart rate targets.

This calculator utilizes the Karvonen Formula, which is widely considered more accurate than simple percentage-of-max calculations because it factors in your individual Resting Heart Rate (RHR). This accounts for your current level of fitness.

Understanding the Math: The Karvonen Formula

The calculation follows three specific steps to find your personalized zones:

  1. Maximum Heart Rate (MHR): 220 – Age.
  2. Heart Rate Reserve (HRR): MHR – Resting Heart Rate.
  3. Target Heart Rate: (HRR × Intensity%) + Resting Heart Rate.

Recommended HIIT Intensity Zones

Training Type Work Intensity Recovery Intensity
Aerobic Intervals 70% – 80% 50% – 60%
Anaerobic/HIIT 85% – 95% 60% – 65%
VO2 Max Sprints 95% – 100% Complete Rest

Interval Training Example

If you are a 30-year-old with a resting heart rate of 65 BPM performing a standard HIIT session at 85% intensity:

  • Max HR: 190 BPM
  • HR Reserve: 125 BPM
  • Work Target (85%): (125 * 0.85) + 65 = 171 BPM
  • Recovery Target (60%): (125 * 0.60) + 65 = 140 BPM

During your work phase, you should aim to reach 171 BPM. During your recovery phase, you should allow your heart rate to drop back toward 140 BPM before starting the next interval.

Tips for Accurate Measurement

For the most accurate results with this calculator, measure your resting heart rate immediately upon waking up in the morning, before consuming caffeine. Use a chest strap monitor during your intervals for real-time accuracy, as wrist-based optical sensors often have a "lag" during rapid changes in heart rate common in interval training.

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