Heart Rate for Hiit Calculator

HIIT Heart Rate Zone Calculator

80% – 85% (Optimal HIIT Start) 85% – 90% (Performance Build) 90% – 95% (Extreme Sprint)

Your Training Profile

Maximum Heart Rate (MHR): –

Heart Rate Reserve (HRR): –

Target HIIT Zone (Work Interval)

–

Note: Your recovery intervals should ideally drop your heart rate back to 60-65% of MHR.

Understanding HIIT Heart Rate Zones

High-Intensity Interval Training (HIIT) is designed to push your cardiovascular system to its upper limits for short bursts. To maximize fat oxidation and cardiovascular improvements (VO2 Max), staying within your specific physiological zones is critical. Using a generic number isn't enough; your age and fitness level (resting heart rate) dictate your unique capacity.

The Karvonen Formula Explained

This calculator utilizes the Karvonen Formula, which is favored by athletes and trainers because it accounts for your Resting Heart Rate (RHR). Unlike simple calculations, the Karvonen method measures the "Heart Rate Reserve"—the actual range your heart has to work with during exercise.

• Step 1: Determine Max HR (220 – Age).
• Step 2: Calculate Heart Rate Reserve (Max HR – Resting HR).
• Step 3: Apply Intensity % to the Reserve and add back the Resting HR.

HIIT Intensity Benchmarks

For a workout to qualify as true HIIT, your "work" intervals should typically fall between 80% and 95% of your maximum capacity. Here is how the levels differ:

80% – 85%: The aerobic-anaerobic threshold. Ideal for longer HIIT intervals (e.g., 4-minute intervals) to build endurance.

85% – 90%: The sweet spot for traditional HIIT (e.g., 1-minute work, 1-minute rest). This triggers the EPOC effect (afterburn).

90% – 95%: Peak performance zone. Reserved for short sprints (20-30 seconds). Requires significant recovery time between sets.

Safety First

Before engaging in high-intensity training, ensure you have a baseline of cardiovascular fitness. If you experience chest pain, extreme dizziness, or shortness of breath beyond the expected exertion, stop immediately and consult a medical professional.

function calculateHIIT() { var age = parseFloat(document.getElementById('hiit_age').value); var rhr = parseFloat(document.getElementById('hiit_rhr').value); var intensityBase = parseFloat(document.getElementById('hiit_intensity').value); if (isNaN(age) || isNaN(rhr) || age < 1 || rhr < 30) { alert("Please enter valid age and resting heart rate values."); return; } // Standard MHR Formula: 220 – age var mhr = 220 – age; // Heart Rate Reserve (HRR) var hrr = mhr – rhr; // Karvonen Formula for target range // Intensity Range = (HRR * %Intensity) + RHR var lowIntensity = intensityBase; var highIntensity = intensityBase + 0.05; var targetLow = Math.round((hrr * lowIntensity) + rhr); var targetHigh = Math.round((hrr * highIntensity) + rhr); // Display Results document.getElementById('res_mhr').innerText = mhr + " BPM"; document.getElementById('res_hrr').innerText = hrr + " BPM"; document.getElementById('res_range').innerText = targetLow + " – " + targetHigh + " BPM"; document.getElementById('hiit_result').style.display = 'block'; // Scroll to result document.getElementById('hiit_result').scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }