How do I actually measure my max HR?

On a hill, after a full warm-up: 3 all-out 3-minute climbs with 2 minutes recovery, then read the highest value of the last one. An all-out 5 or 10 km race also gives a good approximation over the final kilometre. Avoid it if you have any cardiac doubt.

Does my max HR drop with training?

No — it declines with age, very slowly, and training barely changes it. What improves is your ability to hold a high percentage of it, and your resting rate coming down. That is why threshold-anchored zones are more useful to track.

Why is my HR lower on the bike than running?

It is normal: 5 to 10 beats lower for the same effort, because you are seated and less muscle mass is working. In swimming the gap is larger still, up to 15 beats, due to the horizontal position and immersion. A triathlete therefore has three sets of zones, not one.

Should I train in zone 2 all the time?

Around 80 % of the volume, yes. But cardiac “zone 2” is not the zone 2 social media talks about: it is simply easy endurance, the pace at which you can hold a conversation. The remaining 20 % must be genuinely hard, otherwise polarisation achieves nothing.

Heart rate zone calculator

Your five heart rate zones from the best data you have: heart rate reserve, threshold HR or max HR, using the Tanaka formula.

Updated 9 October 2026

In short

Max HR is estimated with the Tanaka formula, 208 − 0.7 × age: 187 bpm at 30, 180 at 40, 173 at 50. It is an average: the standard deviation is about 7 beats, and a max HR measured at the end of an all-out effort is always better.

Heart rate zones work across all four endurance sports: they are the only marker still valid when pace stops meaning anything — uphill, in the water, in heat, or on the bike.

Provided they are built on the right anchor. Three methods exist and they are not equivalent: the best data you have determines which one to use.

Threshold heart rate (bpm)

Average HR over an all-out 30 to 60 minute race

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Estimated max HR by age

Age	Tanaka (208 − 0.7 × age)	“220 − age”
20	194 bpm	200 bpm
25	191 bpm	195 bpm
30	187 bpm	190 bpm
35	184 bpm	185 bpm
40	180 bpm	180 bpm
45	177 bpm	175 bpm
50	173 bpm	170 bpm
55	170 bpm	165 bpm
60	166 bpm	160 bpm
65	163 bpm	155 bpm
70	159 bpm	150 bpm

The “220 − age” formula is shown for comparison: it over-estimates max HR in young people and under-estimates it after 40.

How it is computed

If you know your threshold heart rate (average HR over an all-out 30 to 60 minute race), that is the best anchor: zones are set as a percentage of it. It is the most reliable method, because threshold moves with training while max HR does not.

If you know your max HR and resting HR, the Karvonen formula uses heart rate reserve — the difference between the two. It is more accurate than a plain percentage of max HR, especially for the low zones, because it accounts for your actual resting rate.

If age is all you have, we use Tanaka: 208 − 0.7 × age. Not “220 − age”, which comes from a 1971 eyeball fit never meant as a predictive formula: it over-estimates max HR in young people and under-estimates it after 40 (by 3 beats at 50, 6 at 60). Either way the standard deviation is around 7 beats: a measured max HR always beats an estimate.

The plans built from this number

Running Trail & ultra Triathlon Swimrun All plans

Now the plan that goes with it

These numbers are exactly the ones Endu uses to build a full preparation: phases, volume, detailed sessions, exported to your watch. 14-day trial, cancel any time.

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Frequently asked questions

How do I actually measure my max HR?: On a hill, after a full warm-up: 3 all-out 3-minute climbs with 2 minutes recovery, then read the highest value of the last one. An all-out 5 or 10 km race also gives a good approximation over the final kilometre. Avoid it if you have any cardiac doubt.
Does my max HR drop with training?: No — it declines with age, very slowly, and training barely changes it. What improves is your ability to hold a high percentage of it, and your resting rate coming down. That is why threshold-anchored zones are more useful to track.
Why is my HR lower on the bike than running?: It is normal: 5 to 10 beats lower for the same effort, because you are seated and less muscle mass is working. In swimming the gap is larger still, up to 15 beats, due to the horizontal position and immersion. A triathlete therefore has three sets of zones, not one.
Should I train in zone 2 all the time?: Around 80 % of the volume, yes. But cardiac “zone 2” is not the zone 2 social media talks about: it is simply easy endurance, the pace at which you can hold a conversation. The remaining 20 % must be genuinely hard, otherwise polarisation achieves nothing.