Zone 2 Heart Rate Calculator

What zone 2 actually is

Zone 2 is a physiological state before it is a heart rate. In the laboratory it is the highest steady intensity at which blood lactate stays close to its resting level, roughly below 2 mmol/L, and at which the body burns the largest absolute amount of fat per minute. San-Millan and Brooks showed in 2018 that professional endurance athletes reach their peak fat oxidation at a higher workload and clear lactate far better than less-fit adults, and that this capacity, which they called metabolic flexibility, is trainable. The point of zone 2 training is to spend long, repeated periods at that intensity so the mitochondria in slow-twitch muscle fibers grow in number and efficiency.

Heart rate is a stand-in for all of that. In the common five-zone model, zone 2 is drawn at 60 to 70 percent of maximal heart rate or, as on this page, of heart rate reserve. ACSM's exercise prescription guidelines call 40 to 59 percent of reserve moderate and 60 to 89 percent vigorous, so the Karvonen zone 2 range sits at the top of moderate and the bottom of vigorous, which is exactly where the lactate threshold lives for most trained people. The cheapest check is the talk test: in zone 2 you can speak in complete sentences with a slight effort. If you can only manage a few words, you have left it; if you could sing, you are below it.

The MAF 180 formula, as information

The MAF 180 formula, from Phil Maffetone's coaching method, is the other number people searching for zone 2 usually want. It sets a ceiling of 180 minus your age, then adjusts it: subtract 10 if you are recovering from a major illness or surgery or take medication regularly; subtract 5 if you are injured, have regressed in training, get more than two colds or flu a year, have allergies or asthma, or are just starting or training inconsistently; make no change if you have trained consistently for up to two years without those problems; add 5 if you have trained for more than two years without problems and are improving. Maffetone treats the result as the top of the aerobic training range, with the range running about ten beats below it.

For a 40-year-old who has trained steadily for a year, that gives a ceiling of 140 and a range of 130 to 140, close to the 132 to 144 the Karvonen method gives the same person with a resting rate of 60. The two often agree within a few beats for people in their thirties and forties and drift apart for the very fit, the older and those with unusual resting rates, because MAF ignores both resting and maximal heart rate. It is an empirical rule from coaching practice rather than a validated equation from a peer-reviewed cohort, which is why this page describes it rather than computing it. Used honestly, both are starting points to be corrected by the talk test and, if you want precision, by a lactate test.

Why the maximal heart rate estimate is the weak link

Every heart rate zone inherits the error of the maximal heart rate it is cut from. The Tanaka equation, 208 minus 0.7 times age, was fitted to data from more than 18,000 adults and has a standard deviation of about 10 beats per minute, which means roughly one person in three has a true maximum more than 10 beats away from the prediction. The older 220 minus age rule, attributed to Fox and colleagues in 1971, was never formally derived and overestimates the maximum in young adults while underestimating it in older ones. At 60 the two equations differ by 6 beats; the difference between either and your real maximum can be far larger.

A measured maximum fixes this. The highest number a chest strap records in the last minute of an all-out effort, such as the final climb of a hard race or a supervised maximal test, is a better input than any equation, and the page uses it when you enter it. Resting heart rate has its own rules: take it lying down on waking, before coffee, and average three mornings. Medications matter too. Beta blockers, some calcium channel blockers and other rate-limiting drugs lower both resting and maximal heart rate, so percentage zones built on an age equation are wrong for anyone taking them, and the talk test or a clinician's guidance should replace them. Wrist optical sensors lag and drop out during intervals; a chest strap is the reliable tool for zone work.

How much zone 2, and how it fits with the rest

The 2018 Physical Activity Guidelines for Americans set 150 to 300 minutes of moderate aerobic activity a week, or 75 to 150 minutes of vigorous, as the range where most of the mortality and cardiometabolic benefit accrues, with more giving additional benefit and any amount beating none. Zone 2 work counts squarely as moderate to vigorous activity, and brisk walking is zone 2 for many people who are starting out. Seiler's review of elite endurance training found that the athletes who improve most spend around 80 percent of their sessions at low intensity and the remainder at high intensity, with little time in between, a pattern now called polarized training.

For a non-athlete the practical version is a few sessions a week of 30 to 60 minutes held in the range this page gives, with one harder session if your clinician has no objection, and strength work on other days. The heart rate will drift upward over a long session as you dehydrate and warm up, a phenomenon called cardiovascular drift; holding pace while the number climbs a few beats is normal. If you have heart disease, chest symptoms with exertion, or have not exercised in years, see a clinician before starting structured training, and ask whether an exercise test would be useful before you rely on any formula.

Methodology and sources

The calculator implements the heart rate reserve method described by Karvonen, Kentala and Mustala in 1957, which expresses training intensity as a fraction of the span between resting and maximal heart rate rather than of the maximum alone, so two people of the same age with different resting rates get different zones. Zone 2 is defined on this page as 60 to 70 percent of that reserve, the common five-zone convention, and the page also shows the 50 and 80 percent boundaries. Maximal heart rate comes from the Tanaka, Monahan and Seals equation of 2001, 208 minus 0.7 times age, derived from a meta-analysis of 351 studies plus a laboratory cohort of 514 healthy adults aged 18 to 81, unless you enter a measured maximum, in which case the measured value is used. The equation carries a standard deviation of about 10 beats per minute, and neither it nor the zones are validated for people on rate-limiting medication.

Worked example: a 40-year-old with a resting heart rate of 60. Maximal heart rate is 208 minus 0.7 x 40 = 180 bpm. Heart rate reserve is 180 minus 60 = 120. The zone 2 floor is 60 + 0.60 x 120 = 60 + 72 = 132 bpm, and the ceiling is 60 + 0.70 x 120 = 60 + 84 = 144 bpm. The 50 percent mark is 120 and the 80 percent mark is 156. The same person with a measured maximum of 190 would have a reserve of 130 and a zone 2 range of 138 to 151. For a 65-year-old with a resting rate of 70: maximum 162.5, rounded to 163, reserve 93, zone 2 from 126 to 135.

The result bands are educational orientation, not published cut-offs. They read the zone 2 floor: under 110 bpm usually reflects an older age or a low resting rate from training; 110 to 139 is where most adults land; 140 or more reflects a young age, a high resting rate, or a resting rate taken sitting rather than on waking. None of these is a diagnosis. The physiological definition of zone 2, lactate near baseline and peak fat oxidation, comes from San-Millan and Brooks (2018), and the 80/20 intensity distribution from Seiler (2010). The MAF 180 formula is described from Maffetone's published method page and is not computed, because it has not been validated against measured physiology in a peer-reviewed cohort.

Medical review: Medical review pending. Last updated October 8, 2026.

References

1. Karvonen MJ, Kentala E, Mustala O. The effects of training on heart rate: a longitudinal study. Ann Med Exp Biol Fenn. 1957;35(3):307-315. PMID 13470504
2. Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol. 2001;37(1):153-156. doi:10.1016/S0735-1097(00)01054-8
3. San-Millan I, Brooks GA. Assessment of metabolic flexibility by means of measuring blood lactate, fat, and carbohydrate oxidation responses to exercise in professional endurance athletes and less-fit individuals. Sports Med. 2018;48(2):467-479. doi:10.1007/s40279-017-0751-x
4. Seiler S. What is best practice for training intensity and duration distribution in endurance athletes? Int J Sports Physiol Perform. 2010;5(3):276-291. doi:10.1123/ijspp.5.3.276
5. Maffetone P. The MAF 180 Formula: heart-rate monitoring for real aerobic training. MAF Method. https://philmaffetone.com/180-formula/