Zone 2 Heart Rate Calculator

Zone 2 heart rate training emphasizes building aerobic efficiency by keeping your effort at roughly 60–70% of your heart rate reserve. By blending your resting rate with your age-based maximum, you maintain a consistent rhythm that boosts mitochondrial density, capillary growth, and fat oxidation without drifting into anaerobic fatigue.

The calculator below uses the Karvonen method so that a 35-year-old with a resting heart rate of 58 bpm taps out at a maximum of 185 bpm. Keeping intensity between 60% and 70% of that reserve yields a target zone of about 129 to 149 bpm, perfect for steady aerobic rides or long runs.

How to use the outputs

Once you see the bpm range, choose workouts that keep your heart rate steady in that window for 30–90 minutes. In the example above, maintaining 129–149 bpm means you can talk in short sentences but can't sprint. Logging the average bpm and duration lets you track aerobic load across weeks.

Because Zone 2 invites long, efficient efforts, pair the results with recovery data such as HRV and sleep. When your range drifts upward despite no change in pace, it signals fatigue or inadequate fueling, so dial back the session or add rest.