Heart Rate Zone Calculator (Karvonen)

How heart-rate zones are worked out

Training zones are percentages of your maximum heart rate. The simplest estimate of maximum heart rate is 220 minus your age. The Karvonen method is more personal: it uses heart-rate reserve, which is maximum minus resting heart rate, and adds your resting rate back. Target = resting + intensity × (maximum − resting).

Zone 1 (50–60 percent) is very easy recovery work, zone 2 (60–70 percent) builds aerobic base, zone 3 (70–80 percent) is steady tempo effort, zone 4 (80–90 percent) is threshold work and zone 5 (90–100 percent) is short maximal intervals.

Worked example

A 40-year-old with a resting heart rate of 60 has an estimated maximum of 180, so the reserve is 120. Using Karvonen, 70 percent is 60 + 0.70 × 120 = 144 bpm and 80 percent is 60 + 0.80 × 120 = 156 bpm, so the zone 3 range is 144–156 bpm. Using the simple percentage of maximum instead, 70–80 percent would be 126–144 bpm, which shows why the method matters.

Limits of age-based formulas

The 220 − age formula can be wrong by 10 to 12 beats per minute for an individual. If you train seriously, a supervised field test gives a better maximum. Medicines such as beta blockers lower heart rate, so anyone taking them or with a heart condition should get zones from a doctor.