Which max heart rate estimate this page uses
The default is Tanaka: 208 minus 0.7 times age. It comes from a 2001 meta-analysis of 351 studies covering roughly 19,000 people, and it fits that pooled data better than the older subtraction does, particularly past fifty. The familiar 220 minus age is available as an option because so much published advice assumes it, and because at forty the two agree exactly. They diverge in both directions away from that point: at twenty-five the classic formula reads about four beats high, at sixty-five about eight beats low.
| Age | 220 - age | Tanaka | Difference |
|---|---|---|---|
| 25 | 195 | 191 | classic reads 4 high |
| 40 | 180 | 180 | identical |
| 55 | 165 | 170 | classic reads 5 low |
| 65 | 155 | 163 | classic reads 8 low |
Neither is good at predicting an individual. The residual scatter around either fit is about ten to twelve beats per minute, and that figure is a standard deviation, not a worst case — roughly one person in three sits more than ten beats away from their age-predicted value. A forty-year-old whose true maximum is 195 will find every zone on this page set about eight percent too low, and will spend a training block believing they are working harder than they are.
If you have ever seen a genuinely maximal number on a chest strap — the top of a hill repeat, the last minute of a hard race — enter it. A single honest measurement is worth more than either equation.
Percent of maximum against the Karvonen method
Percent of maximum multiplies your max heart rate by the intensity: seventy percent of 180 is 126. The Karvonen method works from heart rate reserve instead, the span between resting and maximum, and adds it back onto resting. For someone with a max of 180 and a resting rate of 55, the reserve is 125 and seventy percent lands at 55 plus 87.5, which is 143 bpm. Seventeen beats apart, describing the same nominal intensity.
Karvonen is the better description because the bottom of the range is not zero. Your heart does not stop at rest, so treating the whole span from zero to maximum as the working range compresses the low zones downward for everybody and does it most severely for people with low resting rates. Two runners with the same maximum but resting rates of 45 and 75 have genuinely different working ranges, and only the reserve method sees that.
Measure resting heart rate lying still, immediately on waking, before you sit up. A value taken after coffee or after standing runs ten to twenty beats high and will quietly shift every zone on the page.
What zone 2 is and is not
Zone 2 gets disproportionate attention because it is where endurance athletes spend most of their volume — often seventy to eighty percent of weekly hours. The physiological reasoning is sound: sustained low-intensity work drives mitochondrial density and capillarisation with a recovery cost low enough that you can repeat it the next day. The intensity is conversational, and if you cannot hold a sentence you are above it.
What it is not is a fat-burning setting that makes you leaner than harder work does. The proportion of energy drawn from fat is highest at low intensity, but the total energy spent per minute is lower, and body composition responds to total energy balance over weeks rather than to fuel mix during a session. Zone 2 earns its place through recoverability and through what it does to the aerobic system, not through its fuel source.
Wrist optical sensors and where they fail
Wrist-based heart rate is photoplethysmography — it reads blood volume changes through skin — and it degrades in predictable places. Cold hands reduce peripheral perfusion and the signal with it. Arm swing and grip tension during running introduce motion artefacts, and the common failure mode is cadence lock, where the watch reports your step rate instead of your heart rate and holds a plausible-looking wrong number for minutes. Response to sudden intensity change lags by twenty to forty seconds, which is most of a short interval.
For steady aerobic work a wrist sensor is adequate. For threshold and anaerobic intervals, where the whole point is hitting a specific range for a specific duration, a chest strap measures the electrical signal directly and does not have these failure modes.
Risk, stated plainly
Deliberately testing your maximum heart rate means driving yourself to genuine exhaustion, and that is the one session in an endurance programme with meaningful cardiac risk attached. Estimation formulas exist so that most people never need to do it. If you have any diagnosed cardiac condition, an arrhythmia, or a family history of sudden cardiac events, the decision about maximal testing is a clinical one and not yours to make from a web page.
Beta blockers lower both resting and maximum heart rate substantially — commonly by twenty to thirty beats at maximum, and the size of the shift varies by drug and dose. Every zone on this page is wrong for someone taking one, and no correction factor fixes it reliably. The same applies to some calcium channel blockers and to a pacemaker with a rate-response setting. In any of those situations the limits come from your clinician, and rating of perceived exertion is a more useful guide than a number in beats per minute. Chest pain, unusual breathlessness or light-headedness during exercise means stopping, not pushing through to a target range.
Related
Once intensity is set, the volume side follows: average cycling speed and walking distance and calories both use the same activity-average approach, with the same limits.
Questions people ask
My watch shows a heart rate above my calculated maximum. Is something wrong?
Usually not. The formulas describe a population average, and roughly half of any age group has a true maximum above the predicted figure. Seeing a number a few beats over your age-predicted value during hard effort is ordinary, and it is better evidence about your maximum than the formula was — enter it as a measured value. Two things do warrant attention: a reading far above plausible, such as 210 at age fifty, which is more likely a sensor artefact or cadence lock, and a high reading accompanied by chest discomfort, dizziness or breathlessness out of proportion to the effort, which means stopping and getting it looked at.
Is a low resting heart rate a good sign?
In a trained endurance athlete a resting rate in the forties or low fifties is the normal consequence of a larger stroke volume — the heart moves the same blood in fewer beats. It is not itself a health target, and driving the number down is not a goal. What is worth watching is change rather than level. A resting rate that has risen five to ten beats above your own baseline for several consecutive mornings commonly precedes an infection or reflects accumulated training load, and a rate below forty in someone who does not train, or one accompanied by fainting or fatigue, is worth a clinical opinion.
Why do my watch zones differ from these?
Almost always because the platform defines them differently. Some use percent of maximum, some use heart rate reserve, and some use percent of lactate threshold heart rate, which is a different anchor entirely. The zone count varies too — three, five and seven zone schemes are all in circulation, so a given watch zone 3 may not correspond to zone 3 here. Check what your device is anchoring to before you reconcile the numbers, and if it lets you enter a measured maximum and resting rate, do that first.
How do I find my actual maximum heart rate?
A properly conducted test is a graded exercise test in a lab, which is also the version that comes with medical supervision. Field protocols exist — repeated hill efforts, or a hard sustained finish at the end of a long climb — and they typically underestimate, because most people cannot voluntarily reach true exhaustion. Given the risk discussion above, this is not something to attempt because a calculator would like a better input. The practical middle path is to note the highest value you have genuinely seen on a chest strap during a hard race or interval session and use that.