Zone 2 heart rate calculator

The three methods disagree on purpose, and the gaps are worth reading. Percent of max is the loosest convention. Karvonen counts your resting pulse, so a lower resting rate pushes its whole band up. MAF 180 hands you one cap to stay under rather than a window. None of this is medical advice: the formulas are population averages, a lab-measured max beats all of them, and Zone 2 itself is better confirmed by the talk test, where you can speak in full sentences but not sing.