Charles University in Prague uses the European Credit Transfer and Accumulation System (ECTS) which is a workload-based system for measuring and comparing study results. The student is awarded a certain number of ECTS credits for each course which reflects the workload necessary to successfully complete a course. Credits are awarded only when the student has fulfilled the course requirements stated by the teacher, such as regular attendance, activity during the lessons, completion of ongoing tasks etc. The credits are allocated by the individual departments in accordance with the standard workload determined by the respective study and examination regulations whereby one credit equals 30 hours of study.

Most of Charles University faculties use the following grading equivalency table:

Please, note that the Faculty of Social Sciences has adopted their own grading system.

More to that here:

https://fsv.cuni.cz/en/exchange/life/academic-information/exams-and-grading-system.