Zone 2 heart rate: how to actually find yours

What people mean by zone 2 heart rate

Zone 2 heart rate is usually put at roughly 60 to 70 percent of your maximum heart rate, with max heart rate itself commonly guessed as 220 minus your age. It's the pace where you can still hold a conversation, breathing noticeably harder than at rest but not gasping. A 2025 study of 50 cyclists found that fixed heart rate percentages can miss real zone 2 effort by a wide margin, so the number on your wrist is a starting point, not a verdict.

The idea reaches well beyond competitive sport now. It was pushed into the mainstream partly through research on elite cyclists' ability to clear lactate at low intensities, work associated with the exercise physiologist Iñigo San Millán, and amplified by physician Peter Attia's writing on longevity training. Wearable brands followed, and most fitness watches now label a "zone 2" band on their heart rate charts, usually built from the same 220-minus-age style formula.

Why the simple formula is often wrong for you

The formula's weakness is that it assumes everyone's heart responds the same way at the same age, and the data says otherwise. A 2025 study in Translational Sports Medicine tested 50 experienced cyclists against six different ways of marking zone 2, including fixed percentages of max heart rate, blood lactate concentration, and fat-burning intensity. The researchers found the power output at a given zone 2 marker varied by 6 to 29 percent across riders, meaning two cyclists both told they were "at 70 percent of max heart rate" could be doing meaningfully different amounts of work. As the authors put it, "fixed percentages of HRmax offer practical simplicity but may inaccurately reflect metabolic responses."

Part of the problem starts even earlier, at the max heart rate estimate itself. Coaching guides note that measured maximum heart rate commonly differs by 10 to 20 beats per minute between two people of the same age, and sometimes by 30 beats per minute or more. Since zone 2 is calculated as a percentage of that number, an inaccurate max heart rate throws off everything built on top of it.

The talk test and other free ways to check

The cheapest fix is to stop relying on the formula alone. The talk test, holding a conversation at a level where it feels a bit strained but still possible, is the low-tech method both Attia and San Millán have described using themselves day to day, rather than watching a fixed number. It lines up reasonably well with the physiological idea behind zone 2: an effort hard enough to be real training, easy enough to sustain for a long time.

Coaching guides also use a perceived-effort scale, rating zone 2 around a 5 or 6 out of 10, distinctly easier than a hard interval but not a total stroll. None of these checks require equipment, and they correct for the fact that your actual threshold, not your age, is what determines your real zone 2.

How to test it properly if you want precision

For anyone training seriously enough that the difference matters, there are better options than guessing. Uphill Athlete, a coaching organization built around endurance training for mountain athletes, recommends a heart rate drift test: hold a steady, easy effort for about an hour, and if your heart rate drifts upward by more than roughly 5 percent while your pace stays flat, you were working above your real aerobic threshold.

The gold standard is still a lab test: a blood lactate or ventilatory threshold assessment, or a fat-oxidation test using indirect calorimetry. San Millán's own lab reportedly uses a long, stepped ramp protocol to find this threshold, and Attia's writing describes a patient case where a measured fat-oxidation test moved someone's training target from 1.5 to 2.5 watts per kilogram, a shift a generic formula would never have caught. A heart rate reserve calculation (subtracting resting heart rate from max, taking 60 to 70 percent of the difference, then adding resting heart rate back) is a middle-ground option that at least accounts for your own resting rate.

How zone 2 fits with zones 1, 3 and 4

One reason the single-number version of zone 2 feels so shaky is that coaches rarely use it in isolation. Uphill Athlete's framework builds all four zones off your measured aerobic threshold (AeT), not off age: zone 1 runs from about 20 percent below AeT to 10 percent below it, zone 2 runs from 10 percent below AeT up to AeT itself, zone 3 sits between AeT and your anaerobic or lactate threshold, and zone 4 is the hard interval range above that. A well-developed aerobic base shows up as a small gap, often cited at around 10 percent, between AeT and the anaerobic threshold; a bigger gap is treated as a sign of under-trained aerobic fitness. None of that structure depends on your age at all, which is precisely what an age-based formula can't give you.

That threshold isn't fixed forever, either. Coaches generally recommend retesting it every 6 to 10 weeks as fitness changes, since a aerobic threshold measured in January can be meaningfully out of date by summer. A static "zone 2 equals 128 to 142 beats per minute" number calculated once from an age formula will drift out of sync with your actual fitness far faster than most people retest for it.

Who actually needs to bother with this

If you're training for a race or chasing a specific endurance or VO2 max goal, the gap between a generic formula and your real threshold is worth closing with a proper test. If you're exercising for general health, the stakes are lower: a steady, conversational pace, checked against how you feel rather than a precise number, gets most of the benefit people associate with zone 2 cardio. Treat any wearable's "zone 2" label as an estimate built on an estimate, not a diagnosis.

Our take

Zone 2 heart rate is a genuinely useful training concept wrapped in a formula that oversells its own precision. The 60 to 70 percent rule is a reasonable place to start, but the 2025 variability data is a real reason not to treat it as exact, especially if a wearable's zone label is driving your workouts. If you're serious about performance, a threshold test is worth the cost. If you're not, the talk test will tell you most of what you need to know.

This is general information, not medical advice. Talk to a clinician before changing anything, especially if you are pregnant, nursing, or managing a condition.