Heart rate zone calculator

Many watches use broad population-based formulas to determine heart rate zones that do not reflect individual physiology. This calculator helps runners determine training zones based on lactate threshold heart rate (LTHR), which provides a more accurate framework for guiding effort.

Using LTHR-based zones can help runners align workouts with the intended training purpose, improve consistency across sessions, and better interpret heart rate data over time. This tool is designed to support clearer training decisions rather than replace coaching or testing.