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Fitness

Zone 2 Heart Rate Calculator

Zone 2 is defined physiologically and estimated arithmetically. This page shows which anchor your zone came from and how wide the error on it is.

Formula lll-zone2-1.0.08 sources6 stated limitations

This page has no named medical reviewer on file. The equation it implements is published and cited below, but the page itself has not been signed off by a member of the review board, and we do not present it as if it had been.

Enter your numbers

7 questions. Questions that only apply to some people appear once your earlier answers decide that they do.

From your health data

4 of these questions can be answered from lab results and device data you have already connected: Age, Measured maximum heart rate, Threshold heart rate, Resting heart rate. Connect them once in your member account and they arrive here pre-filled and labelled as coming from your health data — and you can always type over the value.

Set up health data in your member account

This public page never reads your health data. Pre-filling happens inside the signed-in app, which is a separate, access-controlled surface.

Zone 2 Heart Rate Calculator inputs
What can you anchor the zone to?

Best first. A measured threshold beats a measured maximum, which beats an age estimate.

From your health data — connect to fill this automatically

The highest value you have seen in an all-out effort, not a device estimate. Optional when you have a threshold heart rate, but it lets the percent-of-maximum definitions be computed too.

From your health data — connect to fill this automatically

Optional. Needed for the heart-rate-reserve (Karvonen) definitions.

All of them are computed and shown; this one is the headline.

More questions will appear once the answers above decide which ones apply.

Nothing you type is stored unless you are signed in and ask us to save it.

How this is calculated

Formula version lll-zone2-1.0.0

Zone 2 is computed as a percentage band of whichever anchor the member can supply: a laboratory or field lactate-threshold heart rate, a measured maximum, or an age-estimated maximum (Tanaka 2001 by default, with the HUNT 2013 equation and 220 - age offered for comparison). Heart-rate-reserve definitions use the Karvonen form, resting + fraction x (max - resting). Eight published definitions are computed side by side, spanning 64% upwards of their respective anchors, because they disagree materially and reporting only one would hide that. Where the anchor is an age estimate, the calculator reports band UNKNOWN: with a standard deviation of 7-11 bpm on estimated maximum heart rate, the resulting range may simply not be zone 2.

What it cannot do

  • There is no consensus definition of zone 2. The eight definitions implemented disagree by more than the width of the zone.
  • Percentages of maximum heart rate do not locate an individual threshold: the first lactate threshold ranged from 70% to 92% of maximum in 165 recreational runners.
  • Tanaka 2001 publishes standard deviations of 7-11 bpm, not a formal standard error. Only the HUNT 2013 equation publishes an explicit SEE (10.8 bpm).
  • 220 - age was never fitted to data and has no published standard error; it is included only to show what it gives and why not to use it.
  • The Gellish 2007 equation is not implemented: its standard error is not published anywhere we could verify.
  • Zone definitions are invalid on rate-limiting medication, in atrial fibrillation, and with a pacemaker.

Sources

  1. Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol 2001;37(1):153-156DOI 10.1016/S0735-1097(00)01054-8 (opens in a new tab)PMID 11153730 (opens in a new tab)
  2. Nes BM et al. Age-predicted maximal heart rate in healthy subjects: The HUNT Fitness Study. Scand J Med Sci Sports 2013;23(6):697-704DOI 10.1111/j.1600-0838.2012.01445.x (opens in a new tab)PMID 22376273 (opens in a new tab)
  3. Robergs RA, Landwehr R. The surprising history of the 'HRmax = 220-age' equation. J Exerc Physiol Online 2002;5(2):1-10View source (opens in a new tab)
  4. Garber CE et al. ACSM position stand: Quantity and Quality of Exercise. Med Sci Sports Exerc 2011;43(7):1334-1359DOI 10.1249/MSS.0b013e318213fefb (opens in a new tab)PMID 21694556 (opens in a new tab)
  5. Seiler S. What is best practice for training intensity and duration distribution in endurance athletes? Int J Sports Physiol Perform 2010;5(3):276-291DOI 10.1123/ijspp.5.3.276 (opens in a new tab)PMID 20861519 (opens in a new tab)
  6. Nuuttila OP et al. Physiological and perceptual responses at the lactate thresholds and the relationship with heart rate reserve in recreational runners. Eur J Appl Physiol 2025;125(8):2161-2171
  7. Jamnick NA et al. An Examination and Critique of Current Methods to Determine Exercise Intensity. Sports Med 2020;50(10):1729-1756DOI 10.1007/s40279-020-01322-8 (opens in a new tab)PMID 32729096 (opens in a new tab)
  8. Karvonen MJ, Kentala E, Mustala O. The effects of training on heart rate; a longitudinal study. Ann Med Exp Biol Fenn 1957;35(3):307-315PMID 13470504 (opens in a new tab)

The formula version is pinned so that a result you saved or shared can be reproduced. When we change a coefficient, the version changes and old results stay attributed to the version that produced them.

Questions people ask

Why does the answer change so much between methods?
Because age-based maximum heart-rate equations are population averages with a standard deviation around 10 to 12 beats per minute. A measured maximum or a field-tested threshold is worth far more than any equation, which is why the tool asks what you have rather than assuming.
Is zone 2 the only thing that matters?
No. The dose-response for mortality is steepest going from nothing to some activity, and high-intensity work raises VO2max faster. Zone 2 is popular because it is sustainable in volume, not because intensity above it is wasted.