The Karvonen method
This calculator uses the Karvonen formula, which factors in your resting heart rate as well as your maximum, giving more personalized training zones than simple percent-of-max methods. It first calculates your heart rate reserve (max heart rate minus resting heart rate), then adds a percentage of that reserve back onto your resting heart rate to define each zone boundary.
Using the zones in training
Triathletes commonly train across five zones spanning easy recovery efforts up to maximal, VO2-max-level efforts. Swim, bike, and run sessions can all be planned around the same zones, though heart rate response can vary slightly between disciplines due to body position and muscle groups used.
- For best accuracy, use a measured max heart rate from a field or lab test rather than an age-based estimate.
- This tool is for general training and educational purposes and does not replace guidance from a coach or physician.
Last reviewed August 2026