Heart Rate Zone Calculator

How to use the heart rate zone calculator

Enter your age and the tool predicts a maximum heart rate, then splits the range below it into five training zones with a beats-per-minute band for each. Adding a resting heart rate is optional and it changes the answer substantially, because it switches the arithmetic from a plain percentage of maximum to the Karvonen heart-rate reserve method.

On a 35-year-old with a resting rate of 60, zone 2 comes out at about 134 to 146 beats a minute; on the same 35-year-old with no resting rate supplied, the same zone reads about 110 to 128. Neither band is wrong. They are two different scales, and the page names which one it used.

Karvonen is the better of the two zone methods when you can feed it a real resting rate, and the reason is structural. A plain share of maximum measures the whole scale from zero beats a minute, a point no living heart ever visits, so the bottom of the scale is anchored to nothing.

Heart-rate reserve measures from your own resting rate up to your maximum instead, which anchors the bottom of the scale to you. Martti Karvonen and colleagues set the method out in Annales Medicinae Experimentalis et Biologiae Fenniae in 1957. For the 35-year-old above, the reserve is 123.5 beats, and zone 1 opens at 122 rather than 92: a difference of 30 beats a minute produced entirely by the choice of scale.

Read the boundaries as soft. Any age-based prediction carries scatter on the order of ten beats a minute in either direction between individuals of the same age, so two 40-year-olds with a genuine maximum of 170 and 190 both get told 180. That spread is a property of human variation, not a flaw in the arithmetic, and it is why a laboratory or supervised field test beats any equation for anyone training seriously.

Why not 220 minus age?

The maximum here comes from the Tanaka equation, 208 minus 0.7 times age, and not from the 220 minus age that most people were taught.

Hirofumi Tanaka, Kevin Monahan and Douglas Seals published it in the Journal of the American College of Cardiology in 2001 after pooling 351 studies covering 18,712 healthy subjects and then validating the result in a separate laboratory cohort. Their finding was that 220 minus age understates the maximum in older adults and overstates it in younger ones.

The formula, worked line by line

Two decisions produce every number on this page. The first is which equation predicts the maximum heart rate, and this tool uses Tanaka rather than the 220 minus age of gym posters and treadmill consoles.

The second is which scale the zone percentages are taken from: the whole distance from zero up to maximum, or the reserve between your resting rate and your maximum. The tool uses the reserve whenever you give it a resting rate, and says which method it applied.

The zone percentages themselves are the conventional five-band scheme: 50 to 60 percent for recovery, 60 to 70 for endurance, 70 to 80 for tempo, 80 to 90 for threshold and 90 to 100 for maximum work. Those cut points are a widely used training convention rather than a physiological law, and different coaching systems draw them in slightly different places.

max HR, Tanaka 2001  = 208 - 0.7 x age
max HR, classic      = 220 - age
heart-rate reserve   = max HR - resting HR
Karvonen zone edge   = resting HR + reserve x percent
percent-of-max edge  = max HR x percent

Run the same 35-year-old without a resting rate and the tool falls back to a plain share of maximum: 183.5 times 0.6 is 110.1 and 183.5 times 0.7 is 128.4, so zone 2 becomes about 110 to 128. Both bands are correctly computed and they differ by roughly 24 beats a minute at the bottom edge.

The reason is that a percentage of maximum implicitly starts its scale at zero beats a minute, while Karvonen starts it where your heart actually idles. The lower your resting rate, the wider the reserve and the further apart the two methods sit.

The honest uncertainty is larger than any of these decimals suggest. Age explains only part of the variation in maximum heart rate, and the residual scatter between individuals of the same age is on the order of ten beats a minute either way, so a predicted maximum of 180 covers real maximums from roughly 170 to 190.

Fitness, altitude, heat, caffeine, illness, dehydration and sleep debt all move a working heart rate on the day, and beta blockers and several other medications lower the whole scale in a way no age equation accounts for. A supervised laboratory test or a structured field test measures what an equation can only predict.

This page is general information, not medical advice and not clearance to train; if you have a heart condition, chest pain, dizziness on exertion, or you are coming back from illness or a long layoff, talk to a doctor before using any of these numbers.

Questions people ask