Target Heart Rate Zone Calculator

Enter an age of 45 and leave the maximum heart rate source on Tanaka.

The calculator estimates maximum heart rate as 208 − 0.7 × 45 = 176.5 bpm and multiplies it by each zone boundary, rounding to the nearest beat. Zone 2, the easy aerobic range most endurance plans are built on, comes out at 106–124 bpm. Zone 4, the hard range used for threshold intervals, is 141–159 bpm.

Switch the source to 220 − age and the maximum becomes 175 bpm. The zones shift by a beat or two — Zone 2 becomes 105–123 bpm and Zone 4 140–158 bpm — because at 45 the two formulas are only 1.5 bpm apart.

If you have done a proper maximal test and seen, say, 182 bpm, choose Measured and enter it. The zones then come from your number rather than an average: Zone 2 becomes 109–127 bpm and Zone 5 tops out at 182. A measured maximum is always better than either formula.

Traditional maximum heart rate: HRmax = 220 − age. It is usually credited to Fox, Naughton and Haskell in 1971, but it was never derived from a formal study designed to predict maximum heart rate. It became standard because it is easy to remember.

Tanaka maximum heart rate: HRmax = 208 − 0.7 × age. Tanaka and colleagues pooled results from 351 published studies covering 18,712 people, then checked the equation in laboratory testing of 514 healthy adults, where they found an almost identical 209 − 0.7 × age. They concluded that 220 − age underestimates maximum heart rate in older adults, and that the relationship did not differ between men and women or with habitual activity level. Below age 40 the Tanaka equation gives the lower figure of the two.

Zone boundaries: bpm = HRmax × percentage ÷ 100, rounded to the nearest whole beat. The five zones are 50–60% (very light), 60–70% (light), 70–80% (moderate), 80–90% (hard) and 90–100% (maximum). The top of one zone is the bottom of the next.

That is everything the calculator does. It does not use resting heart rate. The Karvonen heart rate zone calculator is the more precise Karvonen method: it subtracts your resting heart rate to find your heart rate reserve and takes percentages of that, so two people of the same age with different resting pulses get different zones there, but the same zones here.

The two equations give identical answers at exactly age 40, where both produce 180 bpm. Move away from 40 and they separate.

At age 65, 220 − age gives 155 bpm and Tanaka gives 162.5 bpm, a gap of 7.5 bpm. Every zone moves with it: Zone 2 is 93–109 bpm by the traditional formula but 98–114 bpm by Tanaka, and Zone 4 is 124–140 bpm against 130–146 bpm. Because Tanaka and colleagues found that 220 − age underestimates maximum heart rate in older adults, an older exerciser following the traditional numbers is likely to be training easier than intended in every zone.

At age 25 the gap runs the other way. The traditional maximum is 195 bpm and Tanaka's is 190.5 bpm, so Zone 4 is 156–176 bpm by 220 − age against 152–171 bpm by Tanaka. A younger person gets slightly higher zones from the traditional formula than from Tanaka's, though the difference is smaller than at 65.

Neither answer is your real maximum. The practical lesson is that the older you are, the more it matters which formula you pick, and the more worthwhile it is to check the zones against how the effort actually feels.

Zones 1 and 2 are easy enough to hold a conversation, and they make up most of the training time in endurance plans. Zone 3 is steady and comfortably hard. Zone 4 is the range for sustained hard intervals. Zone 5 can be held only briefly.

Guidelines use broader labels than training zones. The American Heart Association describes moderate-intensity activity as about 50–70% of maximum heart rate and vigorous activity as about 70–85%. Those ranges cut across the five zones — moderate spans Zones 1 and 2, and vigorous covers Zone 3 and part of Zone 4 — and other organisations draw the lines in slightly different places. A five-zone table lets you see where any guideline's range falls on your own numbers: at age 45 with the Tanaka estimate, the AHA's vigorous range is about 124–150 bpm.

Heart rate also lags effort. In a 30-second sprint it may never reach the zone the effort really belongs in, and on a long, hot session it drifts upward even at a constant pace. For short intervals, go by effort or pace; for steady sessions, heart rate is a good guide. Our heart rate zone training guide covers how to build a week around the zones.

It estimates an average. Both formulas describe the typical maximum for a given age, and individuals differ from it substantially. Two 45-year-olds can have real maximums many beats apart with no difference in fitness or health.

Medication and illness change heart rate. Beta blockers and some other drugs blunt the heart rate response to exercise, which makes age-based zones meaningless. Fever, dehydration, heat, caffeine and poor sleep all raise heart rate at a given effort.

It is not a medical exercise prescription. If you have heart disease, high blood pressure that is not controlled, or chest pain, faintness or unusual breathlessness when you exercise, see a doctor before training to heart rate targets.

Wrist sensors can be wrong. Optical heart rate readings are less reliable during intervals and strength work than a chest strap, so a zone reading may reflect the sensor rather than your heart.

If you know your resting heart rate, the Karvonen heart rate reserve calculator personalises these zones further, and the recovery heart rate calculator shows how quickly your heart rate falls after a hard effort, a separate marker of fitness. To see what your aerobic capacity looks like as a number, the VO2 max estimation calculator works from a field test, and the pace calculator turns a zone-based run into target pace and finish times.