Heart rate zone calculator

Maximum heart rate comes from the Tanaka equation, fitted in a meta-analysis of 351 studies (18,712 people) and confirmed in 514 people tested in the laboratory. It held for men and women and for sedentary and trained adults alike. The estimate is rounded to a whole bpm before the zones are worked out.

HRmax    = 208 − 0.7 × age (years)
% of max = round(p × HRmax)
Reserve  = round(rest
           + p × (HRmax − rest))
p        = 0.5, 0.6, 0.7, 0.8, 0.9, 1.0

220 − age is shown for comparison. It is the older rule of thumb, usually credited to Fox and colleagues (1971), and was not derived from a study of its own. The two agree at 40. Above 40, 220 − age gives a lower maximum (150 against 159 bpm at 70), the underestimate in older adults that Tanaka reported.

With a resting heart rate, the zones use heart rate reserve, the method of Karvonen and colleagues (1957) that ACSM uses to set exercise intensity. The reserve is maximum minus resting heart rate; each zone edge is a percent of the reserve added to the resting rate, so the zones sit higher than the same percent of maximum.

The zones and their names:

• Zone 1, very light: 50 to 60%
• Zone 2, light: 60 to 70%
• Zone 3, moderate: 70 to 80%
• Zone 4, hard: 80 to 90%
• Zone 5, maximum: 90 to 100%

Five zones in 10% steps are a common training convention, the one heart rate monitors use, not a clinical standard. For comparison, ACSM classes 64 to 76% of maximum (40 to 59% of reserve) as moderate and 77 to 95% of maximum (60 to 89% of reserve) as vigorous.

Each edge is rounded to a whole bpm, halves up. A zone runs from its lower edge to 1 bpm below the next zone’s, and zone 5 ends at the maximum, so no reading falls in two zones. For example, at age 40 the maximum is 208 − 28 = 180 bpm, and the zones are 90–107, 108–125, 126–143, 144–161 and 162–180 bpm. With a resting heart rate of 60 bpm, the reserve is 120 bpm and zone 2 runs from 60 + 72 = 132 to 143 bpm.