Cold Plunge Calc gives you a safe, personalized plunge time based on your water temperature, experience, and goal — then builds a free 6-week plan toward the ~11 min/week target from Dr. Søberg's research. Every recommendation links to real studies (Harvard Health, PubMed, Cell Reports Medicine). No sign-up, no tracking, no upsells. Your data never leaves your device. Available in 7 languages. 100% free.