Five training zones in bpm, using the Karvonen (heart-rate-reserve) method.
| Zone | Intensity | Heart rate |
|---|
Enter your max heart rate (or age) to see your zones.
This calculator uses the Karvonen method, which bases zones on your heart rate reserve — the gap between resting and maximum heart rate — rather than a simple percentage of max. The formula is: target HR = resting HR + (max HR − resting HR) × intensity%. Because it accounts for your resting heart rate, it personalizes zones better than %max alone: two runners with the same max HR but different fitness levels get different (and more accurate) zones.
If you leave resting HR blank, the calculator falls back to a straight percentage of max HR — less precise but still useful. If you don't know your max HR, enter your age and the calculator estimates it with the Tanaka formula (208 − 0.7 × age), which research shows is more accurate than the traditional "220 minus age".
Age formulas are estimates with a standard deviation of about ±10 bpm. For a real number, look at the highest value your HR monitor has recorded at the end of a hard race or all-out hill repeats. A field test: after a thorough warm-up, run 3 × 2 minutes uphill at maximal effort — the peak reading is close to your true max.
Check your heart rate first thing in the morning before getting out of bed, for several days, and take the average. Most watches with sleep tracking report it automatically.
Zone 2 builds mitochondrial density and fat-burning capacity with low injury risk, so you can accumulate a lot of it. Most successful endurance programs put roughly 80% of training time at or below Zone 2 intensity.
Karvonen (enter both max and resting HR) is more personalized because it accounts for fitness via resting heart rate. Use %max only if you don't know your resting HR. The zones from the two methods can differ by 5–15 bpm at the low end.
Watch vendors use different zone models (some use 5 zones of %max, some use lactate-threshold anchored zones). None is "wrong" — what matters is using one model consistently. This calculator's zones map to common running training language (easy/tempo/threshold/VO2max).