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). Max heart rate can come from three sources: the Tanaka formula, the classic "220-age" formula, or a measured value.
The two zone 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 ≤ HR < 126 bpm with the %HRmax method, but 132 ≤ HR < 144 bpm with the Karvonen method (upper bound excluded, except for Zone 5).
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) or the classic "220 − age" formula - both population estimates, not a personally measured value (see the dedicated comparison section below, and 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
Max heart rate estimate (220-age)
Classic, very common estimate, not a precise or universally validated equation - see the comparison with Tanaka below.
Example
Age 60 → Max HR = 220 − 60 = 160 bpm (Tanaka at the same age: 166 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
Tanaka or 220-age: two different estimates, not interchangeable
The "220 − age" formula is probably the most common max heart rate estimate in practical use, but its origin cannot be reliably traced to a single validated study. The Tanaka formula (208 − 0.7 × age) was published in 2001 specifically to replace it with an estimate based on a meta-analysis of over 18,000 healthy adult subjects. This calculator shows both side by side, so you can see how much they diverge at your age, instead of treating "220-age" as a precise or universally validated value.
The two formulas are not parallel: they coincide exactly at age 40 (220−40 = 180 = 208−0.7×40), but diverge in opposite directions moving away from that age. Example: at age 60, "220-age" gives 160 bpm, Tanaka gives 166 bpm (a 6 bpm difference); at age 20, "220-age" gives 200 bpm, Tanaka gives 194 bpm (6 bpm again, but in the opposite direction).
If you know your max heart rate from a real test, always use "measured" mode: neither estimation formula replaces a directly observed value.
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 ≤ HR < 126 bpm.
Zone 2 (60-70%) with the Karvonen method: 60 + 120×0.60 = 132 bpm, 60 + 120×0.70 = 144 bpm → 132 ≤ HR < 144 bpm.
Same nominal zone, same person, same instant: an 18 bpm difference between the two methods purely from the choice of reference.
Boundary convention: each zone's lower bound is inclusive, its upper bound is exclusive - except for Zone 5, which also includes its upper bound. Example: at exactly 126 bpm (%max heart rate method), the calculator assigns Zone 3, not Zone 2, because 126 is Zone 2's EXCLUDED upper bound and Zone 3's INCLUDED lower bound at the same time - not a gap or an overlap, just an unambiguous assignment rule.
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 Tanaka or with "220-age" 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 either estimate: no formula-estimated value replaces an individual measurement.
The 18-100 year range accepted by the estimate modes is a TECHNICAL limit of this calculator, not a claim that the entire range exactly matches the population studied by Tanaka et al. (who describe their meta-analysis as conducted on "healthy adults", without publishing the exact age limits of every included sub-study). At ages closer to the extremes of this range (near 18 or near 100 years), the estimate calls for particular caution: individual variability around the population average tends to be larger further from the ages most represented in the studies.
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 chosen estimate (Tanaka or 220-age).
Why do you offer both Tanaka and "220-age"? Which should I use?+
"220-age" is the most common estimate in practical use, but its origin cannot be reliably traced to a single validated study. Tanaka (2001) was published specifically to replace it with an estimate based on a larger meta-analysis. The two formulas coincide exactly at age 40 and diverge in opposite directions moving away from that age (see the dedicated section above). If you don't have a measured max heart rate, Tanaka has the stronger evidence base of the two; "220-age" is included here because it's likely the one your device already shows you, for a direct comparison.
Why doesn't the calculator accept a child's age with the estimate modes?+
The Tanaka and "220-age" formulas were developed and verified on adult populations (Tanaka's study explicitly describes its meta-analysis as conducted on healthy adults): applying them to a pediatric age would go beyond the range they are verified for, not because a low age is itself an impossible value. "Measured" mode, on the other hand, does not use or require age at all, since it doesn't enter the calculation.
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 keep compatible heart-rate and workout data in one timeline?
FitMesh Sync brings compatible heart rate and workout data detected by your ring or smartwatch into a single personal timeline. The calculator above remains a separate educational tool: FitMesh does not recalculate or configure your device's heart rate zones.
Discover FitMesh Sync