Karvonen Formula Calculator for Target Heart Rate

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Karvonen Formula Calculator

Measure this first thing in the morning for best accuracy.
Common ranges: 50-60% (Warm up), 60-70% (Fat burn), 70-85% (Aerobic).

Your Results

Target Heart Rate: 0 BPM

Estimated Max Heart Rate: 0 BPM

Heart Rate Reserve (HRR): 0 BPM

function calculateKarvonen() { var age = parseFloat(document.getElementById('ageInput').value); var restingHR = parseFloat(document.getElementById('restingHRInput').value); var intensity = parseFloat(document.getElementById('intensityInput').value); if (isNaN(age) || isNaN(restingHR) || isNaN(intensity) || age <= 0 || restingHR <= 0 || intensity <= 0) { alert("Please enter valid positive numbers for all fields."); return; } // 1. Calculate Maximum Heart Rate (Standard Formula: 220 – Age) var maxHR = 220 – age; // 2. Calculate Heart Rate Reserve (HRR = MaxHR – RestingHR) var hrr = maxHR – restingHR; // 3. Karvonen Formula: Target HR = ((Max HR − Resting HR) × Intensity%) + Resting HR var intensityDecimal = intensity / 100; var targetHR = (hrr * intensityDecimal) + restingHR; // Display Results document.getElementById('targetHRDisplay').innerText = Math.round(targetHR); document.getElementById('maxHRDisplay').innerText = Math.round(maxHR); document.getElementById('hrrDisplay').innerText = Math.round(hrr); document.getElementById('thrResultBox').style.display = 'block'; }

Understanding the Karvonen Formula

When it comes to cardiovascular training, not all heart rate calculations are created equal. While many people use the simple "220 minus age" method, fitness professionals often prefer the Karvonen Formula. This method is considered significantly more accurate because it takes into account an individual's Resting Heart Rate (RHR).

How the Karvonen Formula Works

The Karvonen Formula calculates your Target Heart Rate (THR) by determining your Heart Rate Reserve (HRR). The HRR represents the range between your resting heart rate and your maximum potential heart rate. By incorporating your resting pulse—which often reflects your current fitness level—the formula provides a personalized intensity zone.

Target HR = ((Max HR − Resting HR) × %Intensity) + Resting HR

Why Use This Calculator?

  • Personalization: Two 40-year-olds may have the same Max HR (180), but if one has a resting heart rate of 50 and the other has 80, their training zones should be different.
  • Progress Tracking: As you get fitter, your resting heart rate typically drops. The Karvonen formula adapts to these changes in your physiology.
  • Safety: It prevents overtraining by ensuring you are working within a heart rate zone that matches your specific aerobic capacity.

Intensity Zones Guide

Depending on your fitness goals, you should aim for different intensity percentages:

Zone Intensity % Benefit
Recovery/Warm-up 50% – 60% Active recovery, basic health.
Fat Burning 60% – 70% Weight management, endurance.
Aerobic Zone 70% – 85% Improved cardiovascular fitness.
Anaerobic/Threshold 85% – 95% High intensity, speed, power.

Example Calculation

Imagine a 30-year-old athlete with a resting heart rate of 60 BPM who wants to train at 70% intensity:

  1. Max HR: 220 – 30 = 190 BPM
  2. HRR: 190 – 60 = 130 BPM
  3. Target: (130 × 0.70) + 60 = 151 BPM

In this scenario, the athlete should maintain a heart rate around 151 BPM to achieve their target intensity.

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