Zone2AI estimates your Zone 2 heart rate range, the easy aerobic intensity that builds endurance, using the same method as the Zone2AI app. Give your age, and your resting heart rate if you know it; a max heart rate you have actually measured makes it more precise. You get the range in beats per minute, a plain line on how it was estimated, and the talk test to check it in your next session. It works for running, cycling and walking, for people aged 16 to 90 who train for general fitness. No sign-in is needed.
If you mention a heart condition, chest pain, heart-rate medication or pregnancy, ChatGPT tells Zone2AI only that, so it can decline to give a range; nothing is stored. In those cases Zone2AI gives no range and suggests asking your clinician instead.
Limitations: the range is an estimate for general fitness, not medical advice. Zone2AI covers Zone 2 only, not other heart-rate zones, workout plans or medical questions. The result card includes a link to the Zone2AI app and one to its website.