Strength and cardio · Cardio
Calculate heart-rate zones (Karvonen)
Age and resting pulse. The tool estimates max HR (220 − age) and five zones on the reserve.
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How the calculator works
Fox–Haskell max HR is 220 minus age. Reserve is max HR − resting HR. A 70–80% zone aims at rest + 70–80% of the reserve (Karvonen), not 70% of raw max HR. Tanaka (208 − 0.7×age) exists; we stay on 220 − age because that is the usual request, while calling it approximate.
Formula and method
HRmax = 220 − age
Fox and Haskell’s formula, widely cited, imprecise for one person.
target = HRrest + intensity × (HRmax − HRrest)
Karvonen, with intensity between 0.5 and 1.
No validated chest strap, no exercise test. The 50/60/70/80/90% bounds are a five-zone teaching split, not the only taxonomy (aerobic, threshold, and VO2max bands vary by coach).
Worked example
Age 30, rest 60 bpm
age = 30, rest = 60.
- HRmax = 190.
- Reserve = 130.
- Zone 2 (60–70%): 138–151 bpm.
HRmax 190; zone 2 ≈ 138–151 bpm.
Input notes
- Age
- Age in years. The formula does not split by sex.
- Resting HR
- True resting pulse, not after coffee or a flight of stairs.
Assumptions and limits
Assumptions
- HRmax = 220 − age.
- Five zones in 10% steps.
- Karvonen on the reserve.
Limits
- Not an exercise ECG.
- Medications (beta blockers) are outside the model.
- Not medical advice.
How to read the result
Social-media “zone 2” is not always 60–70% Karvonen. Treat the bounds as a ballpark, then use a strap and how it feels.
Common mistakes
Taking 70% of 190 instead of Karvonen.
70% of 190 = 133; Karvonen 70% = 151 here.
Typing warm-up HR as rest.
Rest is taken in the morning, seated.
Ignoring a cardiac medication.
The formula cannot see it. A clinician comes first.
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Frequently asked questions
What is the Karvonen formula?
Rest + % of (max − rest).
It uses the reserve, not a percent of max HR alone.
Why 220 − age?
It is the most common request.
Individually, true max HR is tested. Tanaka and other formulas exist.
Is zone 2 60–70%?
In this teaching split, yes.
Other coaches place zone 2 differently. There is no single standard.
Author and update
Written by Rédaction HexaCalc (editorial team). Content last updated: August 25, 2026. No third-party medical or financial review is claimed.
This calculation uses a standard mathematical identity. See also the methodology.
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