Heart Rate Zone Calculator

A heart rate training zone is a range of beats per minute (bpm) that corresponds to a specific exercise intensity level. Training in different zones produces different physiological adaptations — lower zones build aerobic base and aid recovery, while higher zones improve speed, power, and lactate threshold.

The Karvonen formula calculates your target heart rate using your Heart Rate Reserve (HRR), which is the difference between your maximum heart rate and your resting heart rate. Because it accounts for your individual resting heart rate, it produces more personalized zones than the basic age-based method. The formula is: THR = [(MHR − RHR) × % Intensity] + RHR.

The most common estimate is the formula MHR = 220 − Age, which is widely used by the American Heart Association. This is a population average and may be off by 10–15 bpm for some individuals. For a more precise result, you can measure your MHR directly by performing an all-out effort test under medical supervision and entering that value into the calculator.

Measure your resting heart rate first thing in the morning before getting out of bed. Count your pulse for 60 seconds, or count for 15 seconds and multiply by 4. Take the measurement on several consecutive days and use the average for the most accurate result. A typical resting heart rate for adults is 60–80 bpm.

Heart rate training is most beneficial when you want to ensure you're working at the right intensity for your goals — building an aerobic base, improving endurance, or managing recovery load. It is especially useful during long, steady-state efforts like easy runs, cycling, or rowing, where effort can be hard to judge by feel alone.

Heart rate can lag behind actual effort during short, high-intensity intervals, and it is affected by factors like heat, humidity, caffeine, stress, and fatigue. In these situations, perceived effort or power output (on a bike) may be a better guide. Heart rate is also less reliable at very high intensities where response time is slow.

Zone 1 (50–60% MHR) is active recovery and very light effort. Zone 2 (60–70%) builds aerobic endurance and fat-burning efficiency. Zone 3 (70–80%) is moderate aerobic training. Zone 4 (80–90%) is the lactate threshold zone that improves speed and performance. Zone 5 (90–100%) is maximum effort used in short, intense intervals to boost power and VO2 max.

Most endurance coaches recommend spending 70–80% of training volume in Zones 1 and 2 (low intensity), with the remaining 20–30% split between Zone 3, 4, and 5 work. This polarized approach maximizes aerobic development while allowing adequate recovery. Spending too much time in Zone 3 (the 'moderate' zone) can lead to fatigue without sufficient high-end stimulus.