Heart Rate Zone Calculator
Your five training zones, from age alone or sharpened with your resting heart rate.
How the zones are computed
Max heart rate is estimated as 220 minus age. Without a resting HR, zones are simple percentages of that max. With one, the Karvonen method takes percentages of your heart rate reserve (max minus resting) and adds resting back, which fits trained individuals much better because fitness lowers resting HR without changing max.
The zones in practice
Zone 2 is where endurance base is built and should feel conversational; most amateurs run it too hard. Zone 4 brackets your lactate threshold, roughly one-hour race effort. The 220-age formula has a standard deviation around 10 bpm, so if your watch regularly sees higher numbers than the estimate, trust the watch and rescale.