FitMesh Labs · Activity
Heart Rate Zones Calculator
Two methods, side by side: %max heart rate and the Karvonen method (%heart rate reserve). Instant in-browser calculation.
Heart rate zones split effort into intensity bands (usually 5), calculated either as a percentage of your maximum heart rate or of your heart rate reserve (max HR minus resting HR, the Karvonen method).
The two methods give different numbers for the same nominal zone: for example, with a max HR of 180 and a resting HR of 60, Zone 2 (60-70%) is 108-126 bpm with the %HRmax method, but 132-144 bpm with the Karvonen method.
Results
Enter your data to see the result.
What heart rate zones are
Heart rate zones are a way to translate perceived effort into a measurable number (beats per minute), split into bands from very light effort to maximal. The 5-zone model used here is the most common in consumer communication (fitness apps, smartwatches, rings), not the only one that exists in the literature.
Each zone corresponds to a percentage range (50-60%, 60-70%, 70-80%, 80-90%, 90-100%): this tool applies the SAME five percentage bands to two different reference points (max heart rate, or heart rate reserve), to show explicitly where the bpm difference you see between devices actually comes from.
The two methods: %HRmax and Karvonen
%Max heart rate method: each zone is simply max heart rate multiplied by the band's percentage (e.g. 70% of 180 = 126 bpm). It ignores your resting heart rate: two people with the same max heart rate but very different resting heart rates (e.g. a trained athlete with a resting HR of 45 and a sedentary person with a resting HR of 75) get exactly the same zones in bpm.
Karvonen method (%heart rate reserve, HRR): the zone is resting heart rate plus the band's percentage of the difference between max heart rate and resting heart rate (e.g. resting 60 + 70% of (180-60) = 60 + 84 = 144 bpm). It accounts for your resting heart rate, so it tends to give more personalized zones - at the same max heart rate, someone with a lower resting heart rate (often fitter) gets slightly higher bpm zones.
Max heart rate: if you have never measured it with a real maximal exercise test, this tool estimates it using the Tanaka formula (208 − 0.7 × age) - a population-average estimate, not a personally measured value (see Limits).
Formulas
Max heart rate estimate (Tanaka)
Used only in "estimate from age" mode.
Example
Age 40 → Max HR = 208 − 0.7×40 = 180 bpm
Zone, %HRmax method
Direct percentage of max heart rate.
Example
Max HR 180, 70% → 126 bpm
Zone, Karvonen method (%reserve)
Percentage of heart rate reserve (max HR minus resting HR), added back to resting HR.
Example
Max HR 180, resting HR 60, 70% → 60 + 120×0.70 = 144 bpm
Why your ring, smartwatch, and apps show different zones
If you have ever compared the zones shown by two different devices during the same workout, they probably do not match - and it is usually not a heart-rate-measurement error, it is almost always a difference in METHOD. Some devices default to the %max heart rate method, others use the Karvonen (%reserve) method only if you have entered a resting heart rate, others anchor zones to a lactate threshold obtained from a dedicated test, and others periodically recalculate resting heart rate and therefore the zones themselves.
None of these methods is "wrong": they are different design choices with real numeric consequences. The same perceived effort can fall into a different nominal zone (e.g. "Zone 2" on one device, "Zone 3" on another) simply because the reference used to compute the percentage is different, not because your body is working differently.
Comparing bpm numbers directly between two devices only makes sense if you know which method each one uses. This calculator shows both methods side by side specifically to make that comparison explicit, instead of leaving you to guess why the numbers do not match.
Full worked example
Age 40 (max heart rate estimated with Tanaka: 208 − 0.7×40 = 180 bpm), resting heart rate 60 bpm (heart rate reserve = 180 − 60 = 120 bpm).
Zone 2 (60-70%) with the %max heart rate method: 180×0.60 = 108 bpm, 180×0.70 = 126 bpm → 108-126 bpm.
Zone 2 (60-70%) with the Karvonen method: 60 + 120×0.60 = 132 bpm, 60 + 120×0.70 = 144 bpm → 132-144 bpm.
Same nominal zone, same person, same instant: an 18 bpm difference between the two methods purely from the choice of reference.
Limits
This tool does not diagnose anything, does not replace a laboratory exercise or lactate test, and is not personalized training advice. It only shows the numbers calculated from the data you enter, with the explicit formula used to obtain them.
The max heart rate estimated with the Tanaka formula is a population average, with real individual variability around the estimate: a person's true max heart rate can differ significantly from the value estimated from age, especially for trained athletes or particular individual conditions. If you know your max heart rate from a real test, use "measured" mode instead of "estimated".
The 5 percentage bands used here (50-60/60-70/70-80/80-90/90-100%) are a common convention, not the only one in the literature or in devices: some systems use 3 zones, others 7, others anchor zones to individually measured lactate thresholds instead of fixed percentages - a further reason why the zone number you see on one device may not match another.
Privacy
All calculation happens in your browser: the age, max heart rate, and resting heart rate you enter are never sent to a server, are not saved by FitMesh, and never appear in the page URL. Closing or reloading the page clears whatever you entered.
CSV export and copying the summary happen locally on your device (direct download or clipboard), with no external service involved.
How to cite this tool
FitMesh Labs, "Heart Rate Zones Calculator" (methodology version 1.0, last reviewed 2026-07-30).
Sources
- Age-predicted maximal heart rate revisited: Tanaka H, Monahan KD, Seals DR - Journal of the American College of Cardiology, 2001. July 30, 2026
- The effects of training on heart rate; a longitudinal study: Karvonen MJ, Kentala E, Mustala O - Annales Medicinae Experimentalis et Biologiae Fenniae, 1957. July 30, 2026
- Assessment of Metabolic Flexibility by Means of Measuring Blood Lactate, Fat, and Carbohydrate Oxidation Responses to Exercise in Professional Endurance Athletes and Less-Fit Individuals: San-Millán I, Brooks GA - Sports Medicine, 2018. July 30, 2026
Frequently asked questions
Which method should I use, %HRmax or Karvonen?+
Neither method is universally "more correct": the Karvonen method accounts for your resting heart rate and is generally considered more personalized, but both remain estimates based on population formulas if your max heart rate is not measured from a real test. The most useful thing is knowing which method the device you already train with uses, so you are not comparing numbers calculated differently.
Why doesn't my ring/smartwatch's Zone 2 match this calculator?+
Because your device probably uses a different method (%HRmax instead of Karvonen, or vice versa), a max heart rate estimated with a different formula than Tanaka's, or zones anchored to a lactate threshold test this calculator does not replicate. See the "Why your ring, smartwatch, and apps show different zones" section above.
How do I enter my real max heart rate instead of estimating it from age?+
Switch to "measured" mode and enter the value you know (from a graded exercise test, a lab test, or the peak observed with a heart rate monitor during a real maximal effort). The calculator will use that value instead of the Tanaka estimate.
What happens if my resting heart rate is close to my max heart rate?+
If the entered resting heart rate is equal to or higher than max heart rate (estimated or measured), the calculation is physiologically impossible: the calculator blocks the result with an error message instead of showing inconsistent zones. A valid but very narrow heart rate reserve instead only produces a non-blocking warning.
Is my data sent or saved anywhere?+
No: the calculation happens entirely in your browser. No network request, no saving to FitMesh servers, no data in the URL.
Want to see your real zones during training?
FitMesh Sync syncs the heart rate detected by your ring or smartwatch into a personal dashboard - no manual calculation every time.
Discover FitMesh Sync