Heart Rate Zone Calculator

The five zones represent increasing exercise intensity measured in beats per minute (bpm). Zone 1 is easy active recovery, Zone 2 is aerobic base building, Zone 3 is sustained aerobic endurance, Zone 4 is threshold training that raises your lactate tolerance, and Zone 5 is maximum-effort anaerobic work near your VO2 max. Each zone targets different physiological adaptations.

The Basic method calculates zones as a simple percentage of your maximum heart rate (MHR = 220 − age). The Karvonen method uses your Heart Rate Reserve (HRR = MHR − resting HR) and adds your resting HR back in, producing zones that account for your individual fitness level. Karvonen zones are generally considered more accurate and personalised, especially for trained athletes.

Measure your resting heart rate first thing in the morning before getting out of bed. Count your pulse for a full 60 seconds, or count for 15 seconds and multiply by four. For best accuracy, take readings on three consecutive mornings and use the average. A typical resting HR is 60–80 bpm; well-trained athletes often see values below 50 bpm.

Heart rate training is most useful for building aerobic base fitness, pacing long endurance sessions, and avoiding overtraining. It works particularly well for Zone 2 easy runs, long-distance events like marathons and triathlons, and recovery days where you need to stay below a ceiling intensity. It is also valuable for athletes returning from injury who need to limit exertion precisely.

Heart rate is less useful for very short, high-intensity intervals where HR lags behind true effort, on very hilly terrain where HR spikes temporarily, in extreme heat or humidity (which artificially elevates HR), or during the first few minutes of a run before HR stabilises. In these situations, pace or power data may be more reliable proxies for effort.

The formula MHR = 220 − age is an average and can be off by ±10–20 bpm for any individual. If your zones feel too easy or too hard, consider taking a maximum heart rate field test (e.g. an all-out 12–15 minute effort) and entering that measured value into the optional Max HR field. Using a measured MHR will give far more accurate zone boundaries.

Zone 2 training (roughly 60–70% of MHR) primarily develops mitochondrial density and fat-oxidation efficiency — the aerobic engine underpinning all endurance performance. Most elite endurance athletes spend 70–80% of total training volume in Zone 2. It also promotes recovery and reduces injury risk compared to high-intensity sessions.

The formulas apply to any aerobic sport, but note that maximum heart rate varies slightly by sport — cycling MHR is typically 5–10 bpm lower than running MHR, and swimming MHR can be 10–15 bpm lower due to the horizontal body position and water cooling. For cycling or swimming, consider using a sport-specific max HR test and entering that value manually for the most accurate zones.