diff --git a/src/main/java/com/classes/dtos/Class/MonthlyCalendarDTO.java b/src/main/java/com/classes/dtos/Class/MonthlyCalendarDTO.java
new file mode 100644
index 0000000..1ede639
--- /dev/null
+++ b/src/main/java/com/classes/dtos/Class/MonthlyCalendarDTO.java
@@ -0,0 +1,31 @@
+package com.classes.dtos.Class;
+
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import java.time.LocalDate;
+import java.util.List;
+import java.util.Map;
+
+@Data
+@AllArgsConstructor
+@NoArgsConstructor
+@Builder
+public class MonthlyCalendarDTO {
+    private int year;
+    private int month;
+    private String monthName; // "Septiembre"
+    private LocalDate firstDayOfMonth;
+    private LocalDate lastDayOfMonth;
+    
+    // Mapa de fecha -> lista de clases en esa fecha
+    private Map<LocalDate, List<CalendarClassDTO>> classesByDate;
+    
+    // Total de clases en el mes
+    private int totalClasses;
+    
+    // Días que tienen clases (para marcar en el calendario)
+    private List<LocalDate> daysWithClasses;
+}
diff --git a/src/main/java/com/classes/services/ClassStatsService.java b/src/main/java/com/classes/services/ClassStatsService.java
new file mode 100644
index 0000000..7fae3a2
--- /dev/null
+++ b/src/main/java/com/classes/services/ClassStatsService.java
@@ -0,0 +1,22 @@
+package com.classes.services;
+
+import com.classes.dtos.Class.CalendarClassDTO;
+import com.classes.dtos.Class.ClassDetailResponse;
+import com.classes.dtos.Class.ClassWithStatsResponse;
+
+import java.time.LocalDate;
+import java.util.List;
+import java.util.UUID;
+
+
+public interface ClassStatsService {
+
+
+    List<ClassWithStatsResponse> getClassesWithStatsByTrainer(UUID trainerId);
+
+    ClassDetailResponse getClassDetail(UUID classId);
+
+    List<CalendarClassDTO> getClassesForCalendar(LocalDate startDate, LocalDate endDate);
+
+    List<CalendarClassDTO> getUpcomingClasses();
+}
diff --git a/src/main/java/com/classes/services/Impl/ClassStatsServiceImpl.java b/src/main/java/com/classes/services/Impl/ClassStatsServiceImpl.java
new file mode 100644
index 0000000..dcccf39
--- /dev/null
+++ b/src/main/java/com/classes/services/Impl/ClassStatsServiceImpl.java
@@ -0,0 +1,184 @@
+package com.classes.services.Impl;
+
+import com.classes.dtos.Class.CalendarClassDTO;
+import com.classes.dtos.Class.ClassDetailResponse;
+import com.classes.dtos.Class.ClassWithStatsResponse;
+import com.classes.dtos.Class.StudentInClassDTO;
+import com.classes.dtos.external.MemberInfoDTO;
+import com.classes.entities.ClassEntity;
+import com.classes.entities.ClassReservation;
+import com.classes.enums.ReservationStatus;
+import com.classes.mappers.ClassStatsMapper;
+import com.classes.repositories.ClassRepository;
+import com.classes.repositories.ClassReservationRepository;
+import com.classes.services.ClassStatsService;
+import com.classes.services.MemberClientService;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+import java.time.LocalDate;
+import java.util.List;
+import java.util.UUID;
+import java.util.stream.Collectors;
+
+@Service
+@RequiredArgsConstructor
+@Slf4j
+public class ClassStatsServiceImpl implements ClassStatsService {
+
+    private final ClassRepository repository;
+    private final ClassReservationRepository reservationRepository;
+    private final ClassStatsMapper classStatsMapper;
+    private final MemberClientService memberClientService;
+
+    @Override
+    @Transactional(readOnly = true)
+    public List<ClassWithStatsResponse> getClassesWithStatsByTrainer(UUID trainerId) {
+        log.info("📊 Obteniendo clases con estadísticas para el trainer {}", trainerId);
+        List<ClassEntity> classes = repository.findByTrainerId(trainerId);
+        return classes.stream().map(classEntity -> {
+            ClassWithStatsResponse response = classStatsMapper.toClassWithStatsResponse(classEntity);
+            long currentStudents = reservationRepository.countByClassEntityIdAndStatus(
+                    classEntity.getId(), ReservationStatus.RESERVADO);
+            response.setCurrentStudents((int) currentStudents);
+            Double avgAttendance = reservationRepository.calculateAverageAttendanceByClassId(classEntity.getId());
+            response.setAverageAttendance(avgAttendance != null ? avgAttendance : 0.0);
+            response.setStatus(determineClassStatus(classEntity, (int) currentStudents));
+
+            return response;
+        }).collect(Collectors.toList());
+    }
+
+    @Override
+    @Transactional(readOnly = true)
+    public ClassDetailResponse getClassDetail(UUID classId) {
+        log.info("🔍 Obteniendo detalle de la clase {}", classId);
+
+        ClassEntity classEntity = repository.findById(classId)
+                .orElseThrow(() -> new IllegalArgumentException("La clase con ID " + classId + " no existe"));
+        ClassDetailResponse response = classStatsMapper.toClassDetailResponse(classEntity);
+        List<ClassReservation> reservations = reservationRepository.findByClassEntityId(classId);
+        List<UUID> memberIds = reservations.stream()
+                .map(ClassReservation::getMemberId)
+                .distinct()
+                .collect(Collectors.toList());
+        List<MemberInfoDTO> membersInfo = memberClientService.getMembersInfo(memberIds);
+        List<StudentInClassDTO> students = reservations.stream()
+                .map(reservation -> buildStudentDTO(reservation, membersInfo))
+                .collect(Collectors.toList());
+
+        response.setCurrentStudents(students.size());
+        response.setStudents(students);
+
+        return response;
+    }
+
+    @Override
+    @Transactional(readOnly = true)
+    public List<CalendarClassDTO> getClassesForCalendar(LocalDate startDate, LocalDate endDate) {
+        log.info("Obteniendo clases para calendario entre {} y {}", startDate, endDate);
+
+        List<ClassEntity> classes = repository.findByClassDateBetween(startDate, endDate);
+        return mapToCalendarDTOs(classes);
+    }
+
+    @Override
+    @Transactional(readOnly = true)
+    public List<CalendarClassDTO> getUpcomingClasses() {
+        log.info("Obteniendo próximas clases");
+
+        List<ClassEntity> classes = repository.findUpcomingClasses(LocalDate.now());
+        return mapToCalendarDTOs(classes);
+    }
+
+    // ==================== MÉTODOS PRIVADOS ====================
+
+    private StudentInClassDTO buildStudentDTO(ClassReservation reservation, List<MemberInfoDTO> membersInfo) {
+        MemberInfoDTO memberInfo = membersInfo.stream()
+                .filter(m -> m.getId().equals(reservation.getMemberId()))
+                .findFirst()
+                .orElse(createDefaultMemberInfo(reservation.getMemberId()));
+
+        List<ClassReservation> memberReservations =
+                reservationRepository.findByMemberId(reservation.getMemberId());
+
+        long totalClasses = memberReservations.size();
+
+        // ✅ Cambiado: uso de Boolean.TRUE.equals() para evitar errores por null
+        long attendedClasses = memberReservations.stream()
+                .filter(r -> Boolean.TRUE.equals(r.getAttended()))
+                .count();
+
+        double attendancePercentage = totalClasses > 0
+                ? (attendedClasses * 100.0 / totalClasses) : 0.0;
+
+        String initials = getInitials(memberInfo.getFirstName(), memberInfo.getLastName());
+
+        return StudentInClassDTO.builder()
+                .memberId(reservation.getMemberId())
+                .name(memberInfo.getFirstName() + " " + memberInfo.getLastName())
+                .email(memberInfo.getEmail())
+                .avatarInitials(initials)
+                .status(memberInfo.getStatus())
+                .membershipType(memberInfo.getMembershipType())
+                .attendancePercentage(attendancePercentage)
+                .totalClasses((int) totalClasses)
+                .lastAccess(memberInfo.getLastAccess())
+                .reservationId(reservation.getId())
+                .build();
+    }
+
+    private List<CalendarClassDTO> mapToCalendarDTOs(List<ClassEntity> classes) {
+        return classes.stream().map(classEntity -> {
+            CalendarClassDTO dto = classStatsMapper.toCalendarDTO(classEntity);
+            long currentStudents = reservationRepository.countByClassEntityIdAndStatus(
+                    classEntity.getId(), ReservationStatus.RESERVADO);
+            dto.setCurrentStudents((int) currentStudents);
+            String action = determineAction(classEntity, (int) currentStudents);
+            dto.setAction(action);
+            return dto;
+        }).collect(Collectors.toList());
+    }
+
+    private String determineClassStatus(ClassEntity classEntity, int currentStudents) {
+        if (!classEntity.isActive()) {
+            return "Cancelada";
+        }
+        if (currentStudents >= classEntity.getMaxCapacity()) {
+            return "Llena";
+        }
+        return "Activa";
+    }
+
+    private String determineAction(ClassEntity classEntity, int currentStudents) {
+        if (!classEntity.isActive()) {
+            return "Cancelada";
+        }
+        if (currentStudents >= classEntity.getMaxCapacity()) {
+            return "Llena";
+        }
+        if (currentStudents >= classEntity.getMaxCapacity() * 0.9) {
+            return "Lista de espera";
+        }
+        return "Reservar";
+    }
+
+    private MemberInfoDTO createDefaultMemberInfo(UUID memberId) {
+        return MemberInfoDTO.builder()
+                .id(memberId)
+                .firstName("Usuario")
+                .lastName("Desconocido")
+                .email("no-disponible@email.com")
+                .status("DESCONOCIDO")
+                .membershipType("N/A")
+                .build();
+    }
+
+    private String getInitials(String firstName, String lastName) {
+        String first = firstName != null && !firstName.isEmpty() ? firstName.substring(0, 1) : "";
+        String last = lastName != null && !lastName.isEmpty() ? lastName.substring(0, 1) : "";
+        return (first + last).toUpperCase();
+    }
+}