Calculator · Intensity
Heart Rate Zone Calculator
Five training zones from three different anchors — threshold heart rate, heart rate reserve, or percentage of maximum — with a clear account of which one to trust.
Your inputs
Zones
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Target heart rate at a chosen intensity
Target
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Three methods, ranked
Zone calculators usually offer one method and present it as fact. There are three in common use and they are not equally good, so the calculator offers all three and this section explains the ranking.
Threshold heart rate — use this one
Your lactate threshold heart rate is the highest heart rate you can sustain in a metabolic steady state, and it is the physiologically meaningful boundary in distance running. Anchoring zones to it means the zone edges correspond to real transitions in fuel use and lactate handling rather than to arbitrary percentages of a number you probably guessed.
Warm up thoroughly. Run thirty minutes as hard as you can hold, alone, on flat ground, at even effort. Take your average heart rate over the final twenty minutes only. That figure is a close practical proxy for lactate threshold heart rate. Repeat it every couple of months; the number should climb as you train.
Karvonen, or heart rate reserve
Karvonen’s method takes the span between resting and maximum heart rate and works in percentages of that span rather than of the maximum alone.
This is a genuine improvement on raw percentage-of-maximum because it accounts for the fact that a runner with a resting heart rate of 45 and one with a resting rate of 70 do not experience the same intensity at 140 beats per minute. Its weakness is that it needs two accurate inputs instead of one, and an error in either propagates through every zone.
Percentage of maximum — the fallback
Simple, ubiquitous, and the least reliable of the three. It ignores resting heart rate entirely and inherits every bit of error in your maximum. Use it when you have nothing better, and treat the boundaries as soft.
Estimating maximum heart rate, if you must
The familiar 220 − age is the weakest option available. Tanaka’s 2001 meta-analysis produced 208 − 0.7 × age, which fits observed data better across adult age ranges, and Gellish and colleagues proposed 207 − 0.7 × age from longitudinal work. For a forty-five-year-old these give 175, 176.5 and 175.5 respectively — reassuringly close to each other, and still carrying an error band of roughly ±11 beats around any individual.
| Formula | Age 30 | Age 45 | Age 60 |
|---|---|---|---|
| 220 − age | 190 | 175 | 160 |
| Tanaka: 208 − 0.7·age | 187 | 177 | 166 |
| Gellish: 207 − 0.7·age | 186 | 176 | 165 |
Notice the formulas diverge most at the ends of the range. Older runners in particular are consistently underestimated by the traditional formula, which is why so many masters athletes are told they are exceeding their maximum heart rate during ordinary tempo runs.
What heart rate cannot tell you
Heart rate is a lagging indicator. At the start of an interval it takes sixty to ninety seconds to catch up with the effort, which makes it nearly useless for controlling short repeats — by the time the number is right, the repetition is over. Run intervals by pace and use heart rate to confirm recovery between them.
It also drifts. Over a long run at unchanging pace, expect heart rate to climb five to ten beats as core temperature rises and plasma volume falls. That is cardiac drift, it is normal, and slowing down to hold a fixed number will turn a steady run into a fade.
And it is noisy. Caffeine, a poor night, a stressful morning, the first hot week of summer and the early hours of a viral infection all move resting and working heart rate by amounts large enough to swamp the training signal. One strange day means nothing. A week of strange days is information.
Common questions
Is 220 minus age accurate?
No, and it never claimed to be. The formula came from a 1971 review of existing data and carries a standard deviation of roughly ten to twelve beats per minute, meaning a substantial share of forty-year-olds have a true maximum anywhere between about 160 and 200. Using it to set zones can misplace every boundary by more than a full zone width.
Why is threshold heart rate better than maximum?
Because it is measurable without a maximal effort, it sits close to the intensities that actually matter for distance running, and it responds to training in a way that maximum heart rate does not. Your maximum is largely fixed by genetics and age; your threshold moves when you train, which is exactly what you want an anchor to do.
My heart rate is higher than usual on easy runs. What happened?
The usual suspects, in rough order of frequency: heat, dehydration, poor sleep, caffeine, illness coming on, and accumulated training fatigue. Cardiac drift also raises heart rate five to ten beats over a long run at constant pace, purely from fluid loss and rising core temperature.
Should I abandon pace and train only by heart rate?
Use both and let them disagree. Pace tells you the mechanical output; heart rate tells you the physiological cost. When cost climbs and output does not, you are either getting tired or getting hot, and both are worth knowing before the session goes wrong.