The formula
How to calculate zone 2 heart rate
Zone 2 is the aerobic base-building intensity most endurance training is built around, calculated here as 60-70% of your heart rate reserve — the gap between resting and maximum heart rate — added back onto your resting rate.
Because this method starts from your resting heart rate, it produces a personalised range rather than a flat percentage of maximum. Someone with a max of 180 and a resting rate of 50 gets a wider, lower Zone 2 (128-141 bpm) than someone with the same max but a resting rate of 70 (144-153 bpm).
What to enter:
- Maximum heart rate (bpm) — from a supervised max test if you have one, otherwise 220 minus your age as a rough estimate
- Resting heart rate (bpm) — measured on waking, before getting out of bed
The result updates on every keystroke. The URL updates too, which makes the filled-in version easy to bookmark or send to someone else.
Consistency in how the underlying measurements are taken matters more than precision to the last decimal — measuring at the same time of day, in the same state of rest or hydration, makes readings taken weeks apart genuinely comparable in a way that a single very precise reading on its own is not.
Why zone 2 heart rate matters
The formula behind zone 2 heart rate comes from published research rather than being invented for this page, and it is presented here exactly as it appears in the literature it is drawn from — the value of a calculator is applying it correctly and instantly, not reinventing it.
Because the calculation depends on a formula rather than a device, it is useful anywhere a scale, a tape measure or a stopwatch is available, without needing specialist equipment — which is also exactly why it should be treated as an estimate rather than a clinical measurement.
None of the figures produced on this page are intended to replace a proper assessment, and nothing here should be read as a diagnosis or a treatment recommendation. What a calculator like this is good for is preparation — arriving at an appointment with an actual number already in hand, rather than a vague sense of a change, tends to make that conversation more useful for everyone involved.
In practice, this kind of figure is often calculated more than once with slightly different inputs to see how sensitive it is — trying a measurement taken this morning against one taken yesterday evening, for instance, to see how much normal daily variation actually moves the result. That habit is a good one: it builds a feel for how much a single reading can be trusted on its own before drawing any conclusion from it.
Worked example
A concrete run-through, using the values already in the fields:
- Maximum heart rate: 180 bpm
- Resting heart rate: 60 bpm
That gives:
- Zone 2 lower limit: 132 bpm
- Zone 2 upper limit: 144 bpm
Those starting figures exist only to show the calculation working, not as a target or a reference value to compare yourself against — replace them with your own measurements in the calculator above and the same formula applies exactly as shown.
Reading the result
If you consistently drift above the upper limit on runs meant to feel easy, that usually signals under-recovery, heat, or simply running the "easy" days too hard rather than a problem with the zone itself.
Where this goes wrong. Using an age-estimated maximum heart rate here compounds two estimates into one — a 10 bpm error in max heart rate shifts both zone boundaries by 6-7 bpm. A measured max from a supervised test gives a meaningfully more accurate zone. This is general fitness information, not medical advice.
As with any general-purpose formula, the result here is an estimate derived from population averages, not a measurement specific to you — a reasonable starting point for a conversation with a qualified professional, not a replacement for one. Nothing on this page is medical advice.
They overlap closely — both sit around 60-70% of heart rate reserve, where fat supplies a large share of energy. The terms come from different traditions (exercise physiology vs. gym marketing) describing much the same intensity.
Most structured plans put the bulk of low-intensity volume there, but not every easy run needs to be capped that strictly — occasional drift into Zone 3 on hills or humid days is normal and not worth chasing down mid-run.
It returns zone 2 lower limit. With 180 bpm maximum heart rate and 60 bpm resting heart rate, that comes to 132 bpm. Change any field and the figure moves with it.
It uses a published formula applied exactly as defined, so the arithmetic itself is precise — but the formula is a population-level estimate, and individual results can vary from it for reasons the formula has no way to account for. Treat the output as a reasonable estimate rather than a measured or diagnostic value.
For most people, yes — a single reading is a snapshot, while the same measurement repeated consistently over weeks or months shows a trend, which is generally more informative than any one figure taken in isolation.
Small differences between calculators usually come down to which published formula or reference dataset each one uses — several equations in this area exist in more than one accepted version. This page states the specific formula used in the section above, so it is possible to check directly whether another source is using the same one.