The 90 Days Schengen app is an Android-based calculator that helps travelers eligible for visa-free entry to the Schengen area, as well as 90-days-multiple-entry Schengen visa holders, calculate their permitted length of stay. The app is ad-free and available in English, Albanian, Arabic, Croatian, French, Georgian, German, Macedonian, Russian, Serbian, Spanish, Turkish, and Ukrainian languages.

It is important to note that the permitted length of stay is not the same as the remaining days, as it takes into account the regained days (the days that will be added while the remainder is being used). The app allows users to store the history of their trips, calculate when they can re-enter in case of overstay, plan exit dates for their ongoing trip (requires subscription), plan their next trip (requires subscription), pick a future control date (requires subscription), set up automatic entry/exit dates fill-in upon crossing the border, set up automatic (weekly) backup to their Google Drive (requires subscription), and manage several user profiles. However, it is essential to remember that the calculator is a helping tool only and does not constitute a right to stay for a period resulting from its calculation.