Zone 2 Heart Rate Calculator
The easy-aerobic zone 2 band (60–70% intensity) from your age — and, when you add a resting heart rate, the Karvonen heart-rate-reserve version alongside it. For the full 50–85% zone ladder, see the Target Heart Rate Calculator; for pacing runs by speed instead, the Pace Calculator.
Your zone 2 band
Example: age 30 → 114–133 bpm (% of max); with resting 60 → 138–151 bpm (Karvonen).
What zone 2 is, and what a formula can produce
On this page zone 2 names one thing, and it is a constant rather than an observation: the 60–70% band at the easy-aerobic end of the intensity ladder. Because it is defined as a percentage, arithmetic can produce it, and that is the whole of what this calculator does. It takes an age, applies the conventional 220 − age rule to estimate a maximum heart rate, and prints 60–70% of that estimate — plus, when a resting heart rate is supplied, the same two percentages run through the Karvonen formula instead.
The same label is also used for a threshold-based quantity, and no formula applied to an age can produce that one: an age is not an observation of the person it describes, and this page receives no observation of anybody. The two are not the same quantity. A calculator can only produce the percentage band, and nothing here is a measurement of the other.
The companion guide — heart-rate zones explained — is the longer read: where 220 − age comes from, how far its spread propagates into every boundary built on it, the full 50–85% ladder, and the algebra behind the two conventions summarized below.
Two methods, deliberately side by side
At age 30 the age-predicted maximum is 190 bpm (220 − age), and 60–70% of it is 114–133 bpm. With a resting rate of 60, the Karvonen formula — (max − rest) × intensity + rest — puts the same percentages at 138–151 bpm. Both examples are computed by the same tested engine as the calculator. The gap is not an error: percent-of-max measures from zero, Karvonen from your resting rate, so the reserve-based band sits higher. Both conventions are in circulation, which is why this page prints both rather than averaging them into a number neither one produced.
The size of that gap is not a matter of opinion either. Expanding the Karvonen expression gives intensity × maximum + resting × (1 − intensity). The first term is the percent-of-max figure; the second is positive at any intensity below 100%. Karvonen is not occasionally the higher number, it is structurally higher, and the term doing the work is largest where the intensity fraction is smallest — the low end of the ladder, which is precisely where zone 2 lives. The guide works that expansion line by line.
Read the two bands above against each other and the consequence is stark: the floor of the Karvonen band sits above the ceiling of the percent-of-max band. They do not merely differ at this age and resting rate, they do not overlap at all. A zone 2 band quoted with no convention attached is therefore ambiguous by more than a rounding step.
Zone 2's edges are two rungs of the 50–85% ladder
The Target Heart Rate Calculator builds the full 50–85% ladder from the same estimated maximum, and prints it by one convention at a time: percent of maximum from an age alone, Karvonen once a resting rate is supplied. Zone 2 is not a separate calculation standing beside that ladder — its floor is the 60% rung and its ceiling is the 70% rung. Asking that same engine function twice at build time puts zone 2's two edges under both conventions: at age 30 the 60% and 70% rungs are 114 and 133 bpm by percent of maximum, and 138 and 151 bpm by Karvonen at a resting rate of 60 — the same four numbers this page prints above. That agreement is checked at build time, so if the two paths ever diverged the site would fail to build rather than publish the discrepancy.
The band across ages, both conventions
One resting rate held at 60 bpm, 5 ages, every figure computed at build time by the same functions the calculator runs in your browser:
| Age | Estimated max (220 − age) | Percent of max, 60–70% | Karvonen, resting 60 |
|---|---|---|---|
| 20 | 200 bpm | 120–140 bpm | 144–158 bpm |
| 30 | 190 bpm | 114–133 bpm | 138–151 bpm |
| 40 | 180 bpm | 108–126 bpm | 132–144 bpm |
| 50 | 170 bpm | 102–119 bpm | 126–137 bpm |
| 60 | 160 bpm | 96–112 bpm | 120–130 bpm |
Two things are visible reading down the columns. The estimated maximum falls by exactly one beat per year of age, because subtracting the age is the entire rule — the convention has no other input and therefore no other behaviour. And the non-overlap holds in every row: the Karvonen floor stays above the percent-of-max ceiling at each of these ages, since the resting term is added back in full while the reserve being scaled shrinks. That property is asserted at build time rather than asserted in prose.
The estimate underneath is the weakest part
220 − age is a population average with wide individual spread — being 10–15 bpm off is common. That is not a defect in the arithmetic, which is exact; it is a property of the input the arithmetic runs on. Because a percent-of-max boundary is nothing more than intensity × maximum, an error in the estimated maximum carries into every boundary in proportion to the intensity.
The rule can be used to show the size of that uncertainty against itself. The convention subtracts one beat per year, so 15 years of age is 15 bpm of estimated maximum — the upper end of the spread commonly reported for a single person. At age 45, percent of maximum puts zone 2 at 105–122 bpm, against 114–133 bpm at age 30: the floor differs by 9 bpm and the ceiling by 11 bpm. Put plainly, the uncertainty attached to one person's estimated maximum spans about as much of this band as 15 years of the convention does.
Three further limits travel with the rule, and none of them appear on the face of a number:
- It was characterized in adults rather than teenagers. Zones computed for a teenager are rough orientation at best. The engine accepts ages from 10 to 100 and will return a band for any of them, but accepting an input is not the same as vouching for what comes out.
- Heart-rate-affecting medication. Medications such as beta blockers make formula zones misleading. A number can still be computed; it no longer means what it appears to.
- A measured maximum always beats the estimate. When one exists from a supervised test, the same 60–70% arithmetic can be applied to it directly, and the largest source of error in this page's output disappears with it.
The resting rate is the only measured input here
Percent of maximum knows one thing about a person: their age. Karvonen knows two, and the second is not an estimate. Holding the age at 30 and moving the resting rate from 50 to 70 bpm moves the Karvonen band from 134–148 bpm to 142–154 bpm.
Two things changed at once. The band moved up, because the resting rate added back at the end of the formula is larger. And it narrowed, from 14 to 12 bpm, because a higher resting rate leaves a smaller reserve for the same 60–70% span to cover. Both effects fall out of the formula rather than out of any judgement about the two entries. Meanwhile the percent-of-max band did not move at all — it never asked for a resting rate, so it cannot respond to one, and it sits unchanged until a birthday.
The engine accepts a resting rate from 30 to 150 bpm and requires it to be below the age-predicted maximum. At or above that value the reserve would not be positive and the Karvonen expression would stop describing a range at all, so the calculator returns an explanation rather than a misleading number.
What the band cannot tell you
A zone 2 band is a pair of arithmetic boundaries derived from an age and, optionally, a resting rate. It describes those boundaries and nothing else. It is not a measurement of the threshold-based quantity the same label is sometimes used for, not a fitness score, and not evidence about how a particular effort went: the arithmetic received two inputs and no observation, so it has no way to notice when the band it printed and the effort it is supposed to mark come apart. That limitation is in the method, not in the reader.
Heart rate is also not the only way to anchor effort. Perceived exertion needs no arithmetic at all, and pace is arithmetic with nothing estimated inside it — the Pace Calculator solves for pace, time, or distance from the other two, and every input it takes is a quantity you measured rather than one a population formula guessed. The heart-rate zones guide sets out the same trade-offs across the whole ladder.
Everything here runs in your browser: nothing you enter is transmitted or stored, and every worked figure above was produced at build time by the same tested functions the calculator calls, from fixed inputs rather than a live reading — so the copy and the code cannot drift apart.
Frequently asked questions
What is zone 2, exactly?
On this page zone 2 is a single constant: the 60–70% intensity band, the easy-aerobic band, applied to an estimated maximum heart rate. Because it is defined as a percentage, arithmetic can produce it from an age alone. The same label is also used for a threshold-based quantity that no formula applied to an age can produce, because an age is not an observation of the person it describes. The two are not the same quantity, and a calculator can only produce the first.
Why do the two methods give different numbers?
Percent of maximum multiplies the estimated maximum by the intensity fraction and stops there. Karvonen scales the heart-rate reserve — the gap between the resting rate and the maximum — and then adds the resting rate back, which lands higher at the same nominal percentage. Neither is more correct; they are different conventions, which is why both are printed rather than averaged into a number no convention produced.
How reliable is 220 − age?
It is a population average with wide individual spread — being 10–15 bpm off is common. It was also characterized in adults rather than teenagers, so a band computed for a teenager is rough orientation at best. A measured maximum from a supervised test always beats the estimate, and the same percentages can be applied to that measured figure directly.
Do I have to enter a resting heart rate?
No. An age alone produces the percent-of-max band. The resting rate is what unlocks the Karvonen column, and it is the only input on this page that is measured rather than estimated. The engine accepts it from 30 to 150 bpm and requires it to be below the age-predicted maximum — at or above that value the reserve would not be positive, so it returns an explanation instead of a number.
Why does my watch show a different zone 2?
Two things vary between one printed band and another, and usually account for it. One is the convention: percent of maximum and Karvonen disagree at the same nominal percentage, by exactly the amount the algebra predicts. The other is the maximum underneath — every boundary is a percentage of whatever maximum it was built from, so a band built on a maximum other than 220 − age is a different band. Which convention and which maximum produced a number usually accounts for the difference.
What if I take a beta blocker?
Medications such as beta blockers make formula zones misleading. A calculator will still return numbers, but those numbers no longer describe intensity the way they otherwise would. That is a question for a qualified healthcare professional rather than for a calculator.
What is zone 2 used for in training plans?
The label names the 60–70% band at the easy-aerobic end of the intensity ladder, and the job of this page ends at converting that label into beats per minute. How much time a plan places in any band is a question about that plan and the person following it, and it is not something arithmetic on an age can answer.
Not medical advice: this calculator provides general educational estimates from published population formulas. It cannot account for your individual health context and must not be used to diagnose or treat any condition — consult a qualified healthcare professional before intensity-based training, particularly with a cardiac condition or heart-rate-affecting medication such as beta blockers. Data is processed locally in your browser and never transmitted. See the methodology page.