Biorhythm Calculator, developed by LunarisApps, is a free Android application that accurately calculates your personal biorhythm predictions for any day you want. The app provides graphical representation of your physical, emotional, intellectual, and intuitive states, along with their percentage values. It also forecasts your tendencies as an arrow. You can add an unlimited number of users and calculate biorhythms for other persons as well. The app recognizes critical days when the curve passes the zero line and predicts the tendency. You can choose to display the rhythms as filled curves or lines and activate or deactivate rhythms. Additionally, the app features settings for average curve, moon phase calculator, journal, calculation of important days, home screen widget, and daily notifications that can be switched off. The app is available in English, German, and Spanish, and has a clean and responsive design with a night mode option.