Heart rate zone calculator
All five zones from Tanaka's max HR formula, plus Karvonen and MAF 180. The difference from every other calculator is that the zone edges here are drawn as bands rather than lines — because an age-predicted max carries a 7–11 bpm standard error, which is most of a zone. Give it a measured max HR and the bands snap shut.
- Z1RecoveryActive recovery and warm-up94–11250–60% HRmax
- Z2Aerobic BaseFat oxidation, mitochondrial density112–13160–70% HRmax
- Z3TempoMuscular endurance, lactate clearance131–15070–80% HRmax
- Z4ThresholdLactate threshold, race pace150–16880–90% HRmax
- Z5VO2 MaxPeak aerobic power, short intervals168–18790–100% HRmax
These edges are bands, not lines. Your zone 2 ceiling calculates to 131 bpm, but on an age-estimated max the honest margin is 124–138 bpm. Zone 2 is only 19 bpm wide, so that margin covers about 74% of the zone. That is the fade on the bars above. Enter a max HR you have actually seen and it disappears.
Against 220 − age
At 30, 220 − age reads 3 bpm high. It runs high for everyone under 40 and low for everyone over.
Both are population averages. Neither gap is bigger than the scatter between two people of the same age, which is the more interesting problem.
How each method works
% Max HR
Zones as a flat percentage of maximum heart rate. Needs one number. Zone 2 is 60–70%, threshold is 80–90%, and everything inherits whatever error is in your max.
Zone HR = MaxHR × %Karvonen (HRR)
Works from heart rate reserve, the gap between resting and max. More personal, but it needs both numbers to be real — a guessed resting HR shifts every zone in the same direction.
Zone HR = (HRR × %) + RestHRMAF 180
Maffetone's aerobic ceiling. A strict, deliberately conservative cap for base training that ignores max HR entirely. Most useful when paired with a repeated MAF test over months.
MAF = 180 − age + adjustmentWhere the numbers come from
What an age formula can and cannot tell you
The estimated max HR here is 208 − 0.7 × age, from Tanaka, Monahan and Seals in the Journal of the American College of Cardiology, 2001. They pooled 351 published studies — 492 group means, 18,712 subjects — then measured max HR directly in 514 more adults to check the line held. It did, and it beats 220 − age, particularly for older adults. That is why this calculator uses it.
What it is not is a statement about you. The r = −0.90 that gets quoted alongside it is the fit to those 492 group averages. Average a few hundred 45-year-olds and you will land close to 177 bpm. One 45-year-old will not. Tanaka's paper publishes no individual-level standard error at all. The studies that do measure that scatter put it at 7–11 bpm for age-based prediction, with most univariate equations above 10 — Robergs and Landwehr, Journal of Exercise Physiology Online, 2002, reviewing two decades of the literature.
Ten beats is not a rounding error at this scale. Each zone spans a tenth of your max — around 18 bpm for most adults. So a boundary drawn from an age formula carries a margin of roughly ±7 bpm, most of a zone's width. Two people the same age can be a full zone apart at the same heart rate. That is why the bars on this page fade at their edges instead of ending in a crisp line: we would rather draw the band than print a number that looks measured when it is modelled.
Karvonen does not fix this
Heart rate reserve is the better method — two people with the same max but different resting rates should not get the same zones. But it adds a second input to get wrong, and a guessed resting HR propagates straight into every zone. Boundaries are rest + % × (max − rest), so a resting HR 10 bpm too high lifts your zone 1 floor by 5 bpm and your zone 2 ceiling by 3 — and it moves every zone the same direction, so nothing cancels. A number you half-remember, or one taken sitting at a desk, is not a resting heart rate. Take it before you get out of bed, five to seven mornings running, and average. A watch tracking you overnight will do this better than you will.
Two things collapse the band
The first is a max HR you have actually seen — the top of a hard hill-repeat session, a race finish, a supervised test. Enter that and the shading disappears, because the number is measured rather than modelled. The second is free: calibrate against how the effort feels. Where the numbers and the feel disagree, the feel is the measurement.
- Z1 Recovery — Easy enough to feel like you are not training
- Z2 Aerobic Base — Full sentences, no gasping
- Z3 Tempo — Short sentences; comfortably hard
- Z4 Threshold — Holds for 30–45 minutes and hurts
- Z5 VO2 Max — Over inside five minutes, one way or another
We have published no research of our own on heart-rate zones, so nothing on this page rests on our data — it rests on the two papers named above. How we handle that distinction generally is in our methodology, and the studies we have run are in the research library.
Frequently asked questions
Is the 220 − age formula accurate?
Not really, and it never was — Robergs and Landwehr traced it back in 2002 and found it was never derived from original research, just eyeballed from a scatter of published data in 1971. This calculator uses Tanaka, Monahan and Seals (2001) instead: 208 − 0.7 × age, from a meta-analysis of 351 studies. The two formulas agree exactly at age 40; below that the old one reads high, above it reads low, by up to 9 bpm at 70. But the more important point is that both are population averages, and neither predicts one person well.
How far off can an age-estimated max HR be?
The studies that report individual scatter put the standard error of estimate for age-based prediction at 7 to 11 beats per minute, with most equations above 10 (Robergs & Landwehr, Journal of Exercise Physiology Online, 2002). Since each zone is only about a tenth of your max — roughly 18 bpm — an error of that size can put you a full zone away from where the formula places you. That is why every boundary on this page is drawn as a fading band rather than a hard line.
Should I use % Max HR or Karvonen?
Karvonen, if you have a real resting HR. It uses heart rate reserve, so two athletes with the same max but different resting rates get different zones, which is closer to how physiology actually works. But it does not remove the uncertainty in your max HR, and it adds a second number to get wrong: a resting HR that is 10 bpm too high lifts your zone 1 floor by 5 bpm and your zone 2 ceiling by 3, in the same direction across every zone. If you are guessing at resting HR, % Max HR is the more honest choice.
What is MAF 180 and when should I use it?
MAF (Maximum Aerobic Function) was developed by Phil Maffetone. The formula 180 − age, with adjustments for training history and health, gives you an aerobic HR ceiling for base training. Many endurance athletes use it as a strict cap for easy runs. It is intentionally conservative, it is not derived from max HR at all, and it works best combined with regular MAF tests over months rather than as a one-off number.
How do I find my true max heart rate?
A supervised max HR test is the most accurate. A common field version: after a 15-minute warm-up, run 3 × 3-minute hard efforts up a hill with 2-minute jogs between. The highest HR you see in the final effort is close to your max. Talk to a coach or doctor before maxing out. Enter that number above and the uncertainty bands on the zones collapse, because the estimate has been replaced by a measurement.
How do I find my resting heart rate?
Take it first thing in the morning, before getting out of bed, after a normal night's sleep. Count beats for 60 seconds. Do this for 5–7 days and take the average. A wrist tracker that samples all night will usually be more reliable than you counting, because it catches the true overnight low rather than a post-waking number.
How much training should I do in each zone?
Most endurance research supports an 80/20 split: about 80% of weekly training time easy (Zones 1–2) and 20% hard (Zones 4–5). Zone 3 is the "grey zone" — too hard to count as recovery, too easy to drive adaptation, and the easiest place to spend a season without meaning to. Note that this distribution assumes your zone boundaries are roughly right, which is exactly what an age formula cannot guarantee.
Should I trust my watch's zones over this calculator?
If the watch has genuinely seen you max out — a race finish, a hard hill session — then yes. Months of measured maxima beat any age formula, including Tanaka. Be careful, though: many devices seed their zones from the same 220 − age or Tanaka estimate you would get here and only update them once they observe something higher. Check what your watch actually has stored before assuming it knows more than the formula.
Read more
Zones are only useful once you know what each one is for. The explainer and the research library go into where these boundaries come from and how much of your week belongs in each.