Heart Rate Zone Calculator - Karvonen, Tanaka & 220-Age

Two numbers decide every zone

Every heart rate zone chart is built from your maximum heart rate, and the better ones also use your resting heart rate. Get those two numbers right and the zones follow. Get max HR wrong by 12 beats and every zone is wrong by the same margin.

Max HR is usually estimated from age. The classic rule is 220 - age, credited to Fox and colleagues in 1971. It was never derived from a proper study; it was a line drawn through a handful of data points. In 2001, Tanaka, Monahan, and Seals published a meta-analysis of 351 studies (18,712 people) in the Journal of the American College of Cardiology and confirmed it in a lab group of 514 healthy adults. Their equation, 208 - 0.7 x age, fits better, especially after 40, where 220 - age underestimates. It also found max HR depends mostly on age, not on sex or fitness.

That is why this calculator defaults to Tanaka. If you have hit a true max in a lab test or at the end of an all-out hill repeat with a chest strap, choose "I know my max HR" and enter it. A measured number beats any formula.

Percent of max vs. Karvonen

The simple method takes a percentage of max HR: zone 2 at 60-70% of max is max x 0.6 to max x 0.7. The American Heart Association uses this framing for its general targets: 50-70% of max for moderate exercise and 70-85% for vigorous.

The Karvonen method (Karvonen, 1957) works on heart rate reserve, the gap between your resting and max HR: target = (max HR - resting HR) x % + resting HR. It matters because two people with the same age and max HR can have very different resting rates. A fit runner resting at 48 bpm and a beginner resting at 80 bpm should not get the same zone 2. Karvonen shifts every zone up for people with higher resting heart rates, and its percentages track oxygen use more closely than raw % of max.

The table shows both methods side by side. Karvonen zones are always higher than % of max zones at the same percentage, which surprises people. That is by design: 60% of reserve is a harder effort than 60% of max.

Worked example

A 55-year-old with a resting heart rate of 60 bpm. Tanaka max HR: 208 - 0.7 x 55 = 169.5 bpm. The old 220 - age rule says 165, about 5 beats lower.

Zone 2 by % of max: 169.5 x 0.60 = 102 bpm to 169.5 x 0.70 = 119 bpm. Zone 2 by Karvonen: reserve is 169.5 - 60 = 109.5, so (109.5 x 0.60) + 60 = 126 bpm to (109.5 x 0.70) + 60 = 137 bpm. Same person, same zone name, a 20-beat difference in the target. The AHA moderate range for this person is 85-119 bpm and vigorous is 119-144 bpm.

How to measure resting heart rate properly

Take it in the morning before you get out of bed, after a normal night's sleep, sitting or lying still. Count your pulse for a full 60 seconds, or read it from a watch. Do this on three or four mornings and average them. A single reading after coffee or a stressful commute can be 10 beats high, which drags every Karvonen zone up with it.

Most adults rest between 60 and 100 bpm; trained endurance athletes often rest in the 40s or 50s. If yours is regularly above 100 at rest, or under 50 with dizziness or fatigue, mention it to a doctor.

Common mistakes

Treating the formula as fact. Age equations predict a group average; individuals commonly land 10 or more beats above or below their predicted max. If zone 2 feels like gasping or zone 4 feels easy, your max is probably off. Trust the talk test: in zone 2 you can speak in full sentences.

Using wrist readings during intervals. Optical wrist sensors lag and can lock onto your running cadence. For short, hard efforts a chest strap is far more accurate.

Ignoring medication. Beta-blockers lower both resting and max heart rate, so age-based zones will ask for efforts you cannot reach and should not chase. If you take heart or blood pressure medication, get a target from your clinician or use perceived exertion instead.

Chasing zone 5 every session. Most endurance plans put roughly 80% of weekly time in zones 1-2. Hard days work because easy days are actually easy.