Transparent by design — computed in your browser from a published formula, not a black box. Verified 2026-05-25. Based on: Karvonen (1957) ↗ · Tanaka HRmax revisited (2001) ↗ Full methodology →
CARDIO · HEART RATE
Heart Rate Zone Calculator
Calculate personalized training zones with the Karvonen method.
Result
Training zones
Karvonen target heart rates across the five training intensity bands.
How to use it
- Measure resting heart rate immediately after waking before getting out of bed (count pulse for 60 full seconds). Average 3 consecutive mornings for the most reliable baseline input for the Karvonen formula.
- Read your five zones: Z1 (recovery), Z2 (aerobic base — conversational), Z3 (tempo — challenging), Z4 (threshold — hard), Z5 (VO2 max — maximum). Zone boundaries are estimates ±5 bpm.
- Zone 2 is underused by most recreational athletes. Spending 70–80% of weekly training volume in Zone 2 (you can speak in full sentences) builds aerobic base, improves fat oxidation, and reduces injury risk over the long term.
- High-intensity work (Zone 4–5) should occupy no more than 20% of total training volume. More than this without sufficient Zone 2 base leads to performance plateau and elevated injury risk.
- Re-run this calculator every 2–3 months of consistent training. Improved cardiovascular fitness lowers resting heart rate, which shifts all zone boundaries — keeping your intensity calibrated to current fitness level.
Questions people usually ask
Which formula is used here?
Uses max heart rate and resting heart rate reserve (Karvonen) to build five intensity zones.
Can I use metric or imperial units?
Yes. This tool supports both metric and imperial units and remembers your preference.
Is this medical advice?
No. This tool provides general fitness estimates and should not replace medical guidance.
Is this tool free and private to use?
Yes. AI Fit Hub tools are free, no-signup browser tools. Inputs stay in your browser unless you choose to share a URL.
Do these tools replace medical guidance?
No. These outputs are general fitness estimates — not medical advice.
Can I switch between metric and imperial units?
Yes. Every tool supports both systems and remembers your preference in localStorage.
Formula
See the math
The underlying formula with variables defined, derivation shown, and a worked example with units.
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