Heart Rate Zone Calculator
Enter your age and resting heart rate to get your five training zones — personalized by the Karvonen method instead of one-size-fits-all percentages.
Resting HR: measure first thing in the morning before getting up, over a few days, and average it. Leave max HR blank to use the age estimate.
How the math works
zone threshold = resting HR + intensity × (max HR − resting HR)
Plain age-based zones treat a trained athlete and a couch potato identically, which is obviously wrong. The Karvonen method works from your heart rate reserve — the span between resting and maximum — so the person with a resting rate of 45 gets different, more honest zones than the person at 75. It's the standard method used by most modern training platforms.
What each zone is for
| Zone | Intensity (% of reserve) | Feels like / used for |
|---|---|---|
| Z1 | 50–60% | Very easy — warm-up, recovery days |
| Z2 | 60–70% | Conversational — aerobic base, fat burning, most of your weekly volume |
| Z3 | 70–80% | Steady — tempo work, comfortably hard |
| Z4 | 80–90% | Hard — threshold intervals, 10K race effort |
| Z5 | 90–100% | Maximal — VO2max intervals, sprint finish |
FAQ
- Why do I spend so much time in Zone 3 when I run?
- Almost everyone's "easy" pace is really moderate. Slowing easy runs down until they genuinely sit in Z2 is the single most common coaching fix.
- Do wrist optical monitors count accurately?
- For steady running, roughly yes. For intervals and cold weather, a chest strap is meaningfully better.
- Do zones change as I get fitter?
- Yes — resting HR drops and the same pace moves down a zone. Re-measure resting HR monthly and rebuild the zones.
This tool provides general information only and is not medical advice. If you have a heart condition or take beta-blockers, ask a doctor before training by heart rate.