Formula to Calculate Heart Rate

Heart Rate Zone Calculator

If left blank, the standard calculation (220 – Age) will be used. Entering this enables the more accurate Karvonen formula.

Whether you are an elite athlete or just starting your fitness journey, understanding your heart rate metrics is crucial for safe and effective training. By calculating your Maximum Heart Rate (MHR) and identifying your specific training zones, you can tailor your workouts to burn fat, build endurance, or improve maximum performance.

How to Calculate Maximum Heart Rate (MHR)

The most common starting point for heart rate training is determining your Maximum Heart Rate. While a clinical stress test is the gold standard, mathematical formulas provide a solid baseline for most people.

1. The Fox Formula (Standard)

This is the most widely used formula due to its simplicity. While generally effective for the average population, it can sometimes underestimate MHR for older, fit adults.

Formula: MHR = 220 - Age

Example: For a 40-year-old, the estimated MHR is 220 – 40 = 180 bpm.

2. The Tanaka Formula

Research suggests this formula is more accurate for a wider range of ages.

Formula: MHR = 208 - (0.7 × Age)

The Karvonen Formula: Adding Accuracy

The standard "220 minus age" formula does not account for individual fitness levels. A 30-year-old marathon runner and a 30-year-old sedentary individual will have the same MHR calculation but vastly different cardiovascular capabilities.

The Karvonen Method incorporates your Resting Heart Rate (RHR) to calculate your Heart Rate Reserve (HRR). This provides training zones that are much more personalized to your current fitness level.

Step 1: Calculate HRR
Heart Rate Reserve = Maximum Heart Rate - Resting Heart Rate

Step 2: Calculate Target Zone
Target HR = (Heart Rate Reserve × Intensity %) + Resting Heart Rate

Understanding Heart Rate Training Zones

Once you have your numbers, training becomes about staying in the right zone for your goals:

• Zone 1 (Very Light, 50-60%): Used for warm-ups, cool-downs, and active recovery. It helps with blood flow and recovery without straining the body.
• Zone 2 (Light, 60-70%): Often called the "Fat Burning Zone." The body becomes more efficient at oxidizing fat and transporting oxygen. You should be able to hold a conversation easily.
• Zone 3 (Moderate, 70-80%): Improves aerobic capacity and endurance. Breathing becomes heavier, and it is harder to hold a conversation.
• Zone 4 (Hard, 80-90%): The anaerobic threshold. This zone improves high-speed endurance and lactate tolerance. It is uncomfortable and sustainable only for shorter periods.
• Zone 5 (Maximum, 90-100%): Maximum effort for sprinting and interval training. This develops maximum performance and speed but carries a higher risk of injury if overused.

When to Re-Calculate

Your heart rate zones aren't static. As you get fitter, your Resting Heart Rate will likely decrease, and your ability to sustain higher heart rates will improve. It is recommended to re-test your Resting Heart Rate every 4-6 weeks (measure it first thing in the morning before getting out of bed) and update your calculations to keep your training effective.

function calculateHeartRate() { // Get inputs var ageInput = document.getElementById('hr_age'); var rhrInput = document.getElementById('hr_resting'); var resultContainer = document.getElementById('hr_result_container'); var maxDisplay = document.getElementById('hr_max_display'); var zoneBody = document.getElementById('hr_zone_body'); // Parse values var age = parseFloat(ageInput.value); var rhr = parseFloat(rhrInput.value); // Validation if (isNaN(age) || age 120) { alert("Please enter a valid age between 1 and 120."); return; } // Calculate Max Heart Rate (Standard Formula 220 – Age) var mhr = 220 – age; maxDisplay.innerHTML = mhr; // Determine if using Karvonen (if RHR is valid) var useKarvonen = false; if (!isNaN(rhr) && rhr > 20 && rhr < mhr) { useKarvonen = true; } // Zone Definitions var zones = [ { name: "Zone 1 (Very Light)", minPct: 0.50, maxPct: 0.60, benefit: "Warm up, Recovery" }, { name: "Zone 2 (Light)", minPct: 0.60, maxPct: 0.70, benefit: "Fat Burning, Basic Endurance" }, { name: "Zone 3 (Moderate)", minPct: 0.70, maxPct: 0.80, benefit: "Aerobic Fitness, Stamina" }, { name: "Zone 4 (Hard)", minPct: 0.80, maxPct: 0.90, benefit: "Anaerobic Capacity, Speed" }, { name: "Zone 5 (Maximum)", minPct: 0.90, maxPct: 1.00, benefit: "Max Effort, Power" } ]; // Build Table HTML var html = ""; for (var i = 0; i < zones.length; i++) { var zone = zones[i]; var minBpm, maxBpm; if (useKarvonen) { // Karvonen Formula: (HRR * %) + RHR // HRR = MHR – RHR var hrr = mhr – rhr; minBpm = Math.round((hrr * zone.minPct) + rhr); maxBpm = Math.round((hrr * zone.maxPct) + rhr); } else { // Standard Formula: MHR * % minBpm = Math.round(mhr * zone.minPct); maxBpm = Math.round(mhr * zone.maxPct); } html += ""; html += "" + zone.name + ""; html += "" + (zone.minPct * 100) + "% – " + (zone.maxPct * 100) + "%"; html += "" + minBpm + " – " + maxBpm + " bpm"; html += "" + zone.benefit + ""; html += ""; } // Output table zoneBody.innerHTML = html; // Show results resultContainer.style.display = "block"; }