Heart Rate Zones for Weight Loss Calculator

To calculate your specific "Fat Burn" zone, please enter your age and your resting heart rate. This tool uses the Karvonen Formula, which is widely considered more accurate than age-only calculations as it accounts for your baseline fitness level.

Current Age (years)

Resting Heart Rate (BPM) Measure while sitting quietly for 5 mins.

Your Personalized Target Zones

Weight Loss / Fat Burn (Zone 2)

60% – 70% intensity. Best for building metabolic efficiency and burning fat.

Aerobic / Cardio (Zone 3)

70% – 80% intensity. Improves cardiovascular fitness and endurance.

Max Heart Rate

Heart Rate Reserve

function calculateHRZones() { var age = parseFloat(document.getElementById('userAge').value); var rhr = parseFloat(document.getElementById('restingHR').value); if (isNaN(age) || isNaN(rhr) || age <= 0 || rhr <= 0) { alert('Please enter valid positive numbers for age and resting heart rate.'); return; } // Calculations using Karvonen Formula var maxHR = 220 – age; var hrr = maxHR – rhr; // Zone 2 (60-70%) – Fat Burn var fatBurnLow = Math.round((hrr * 0.60) + rhr); var fatBurnHigh = Math.round((hrr * 0.70) + rhr); // Zone 3 (70-80%) – Aerobic var aerobicLow = Math.round((hrr * 0.70) + rhr); var aerobicHigh = Math.round((hrr * 0.80) + rhr); // Update UI document.getElementById('maxHR').innerText = maxHR + " BPM"; document.getElementById('hrReserve').innerText = hrr + " BPM"; document.getElementById('zoneFatBurn').innerText = fatBurnLow + " – " + fatBurnHigh + " BPM"; document.getElementById('zoneAerobic').innerText = aerobicLow + " – " + aerobicHigh + " BPM"; document.getElementById('hrResults').style.display = 'block'; }

How Heart Rate Zones Impact Weight Loss

Understanding your heart rate zones is essential for optimizing your workouts. While "calories in vs. calories out" is the foundation of weight loss, the intensity of your exercise determines which energy source your body prioritizes.

The "Fat-Burning Zone" (Zone 2)

This zone typically sits between 60% and 70% of your maximum heart rate. At this intensity, your body derives a higher percentage of calories from stored fat rather than glycogen (carbohydrates). It is sustainable for longer durations, allowing you to burn more total fat over a 45–60 minute session.

The Aerobic Zone (Zone 3)

Between 70% and 80% intensity, you enter the Aerobic Zone. Here, you burn more total calories per minute than in Zone 2, but a higher ratio of those calories comes from carbohydrates. This zone is critical for improving your VO2 max and overall heart health.

Weight Loss Strategy Example

Beginners: Aim for 30 minutes in Zone 2 (Fat Burn), 3-4 times per week.
Intermediate: Mix 2 sessions of Zone 2 (45-60 mins) with 1-2 sessions of Zone 3 (30 mins).
Advanced: Use Zone 2 for active recovery days to keep the metabolism elevated without overtraining.

Note: The 220-age formula is a statistical average. Individual results may vary based on fitness level, medications (like beta-blockers), and genetics. Always consult a physician before starting a new vigorous exercise program.