diff --git a/studymanager/src/main/java/io/redlink/more/studymanager/service/StudyService.java b/studymanager/src/main/java/io/redlink/more/studymanager/service/StudyService.java
index 336accdf..60b438e2 100644
--- a/studymanager/src/main/java/io/redlink/more/studymanager/service/StudyService.java
+++ b/studymanager/src/main/java/io/redlink/more/studymanager/service/StudyService.java
@@ -223,7 +223,7 @@ public Optional<Duration> getStudyDuration(Long studyId) {
                                                 java.time.Period.between(
                                                         Objects.requireNonNullElse(study.getStartDate(), study.getPlannedStartDate()),
                                                         Objects.requireNonNullElse(study.getEndDate(), study.getPlannedEndDate())
-                                                ).getDays())
+                                                ).getDays() + 1)
                                         .setUnit(Duration.Unit.DAY)
                                 ))
                 );