The Karvonen Formula is a heart-rate training method that uses both your maximum heart rate and your resting heart rate to calculate more personalized cardio zones.

Instead of only using a percentage of your max heart rate, it calculates your heart rate reserve, which is the difference between your max heart rate and resting heart rate.

Formula:
Target HR = ((Max HR − Resting HR) × Intensity) + Resting HR

This makes the zones more individualized and useful for endurance training, fat loss, aerobic conditioning, and performance tracking.