Heart Rate Zones Calculator (Karvonen Method)
Calculate your five training heart rate zones from age and resting heart rate using the Karvonen heart-rate-reserve formula.
What this calculates
Training zones map workout intensity to physiological adaptations: Zone 1 = recovery, Zone 2 = aerobic base, Zone 3 = tempo, Zone 4 = threshold, Zone 5 = VO2 max. The Karvonen method uses heart-rate reserve (max minus resting) and is more accurate than simple percentage-of-max formulas, especially for fit people with low resting heart rates.
Formula & how it works
Max heart rate (MHR) ≈ 208 − 0.7 × age (Tanaka formula; more accurate than the old '220 − age'). Heart rate reserve (HRR) = MHR − resting HR. Zone target = resting HR + zone_percent × HRR. Zones: 1 (50–60 % HRR), 2 (60–70 %), 3 (70–80 %), 4 (80–90 %), 5 (90–100 %). Verify your real MHR with a max-effort test — formula MHR can be off ±10 bpm.
Worked example
35-year-old, resting HR 55 bpm. MHR = 208 − 24.5 = 183.5 bpm. HRR = 183.5 − 55 = 128.5. Zone 2 (60–70 % HRR): 55 + 0.60 × 128.5 = 132 to 55 + 0.70 × 128.5 = 145 bpm. Most aerobic 'base' work happens in Zone 2 — easier than it feels for many beginners.
Frequently asked questions
Why use Karvonen instead of % of max?
% of max ignores resting heart rate. Karvonen accounts for it via HRR, so a fitter person with a low resting HR gets appropriately lower zone targets. The two methods give similar zones at 85 % effort but diverge in lower zones.
How do I find my real max heart rate?
Formula MHR is an estimate. To find your true MHR: warm up thoroughly, then run hard for 4–5 minutes with a chest-strap monitor. The peak you reach is roughly your MHR. Repeat on a different day to confirm.
How much time in each zone?
Polarized training research suggests ~80 % of total time in Zone 2 (easy aerobic), and ~20 % in Zones 4–5 (hard). Zone 3 'no man's land' is often overdone by recreational athletes because it feels productive without being efficient.
Is the talk test a good substitute?
Yes for rough zones. Zone 2 = full conversation possible. Zone 3 = short sentences. Zone 4 = single words. Zone 5 = can't talk. Useful when you forget your heart-rate monitor.
Disclaimer: Informational only. If you have heart issues or are over 40 starting a new program, talk to a doctor first.