Heart Rate Zone Calculator

Heart Rate Zone Calculator

Heart rate zones identify how hard your cardiovascular system is working and help you tailor workouts for recovery, endurance, tempo, threshold, and VO₂ max efforts. This calculator uses your age, resting heart rate, and an optional measured maximum heart rate to personalize the Karvonen formula so you hit the right beats per minute for each zone.

Understanding Each Zone

Zone 1 keeps your body primed for recovery and ensures your nervous system resets without overstressing muscles. Zone 2 builds aerobic endurance, teaching mitochondria to use fat as fuel. Zone 3 introduces tempo efforts that raise your lactate threshold, while Zone 4 pushes you near race pace so you can sustain higher intensities. Zone 5 represents short anaerobic bursts to improve your VO₂ max and sprint capacity.

Training with heart rate zones prevents overtraining and ensures long-term cardiovascular progress. Listen to perceived effort and adjust the duration of each zone; for example, a long run in Zone 2 can last over an hour, while Zone 5 efforts should be 30–90 seconds with ample recovery.

Example Scenario

For a 35-year-old athlete with a resting heart rate of 58 bpm and an estimated maximum of 185 bpm (220 minus age), the calculator shows each zone range. Zone 2 would span roughly 117 to 132 bpm, giving a concrete target for steady aerobic runs, while Zone 4 would sit around 149 to 164 bpm for interval training. These numbers help you balance intensity and recovery in structured workouts.