diff --git a/app/controllers/grades_controller.ts b/app/controllers/grades_controller.ts
index b0c4088..a95cc9e 100644
--- a/app/controllers/grades_controller.ts
+++ b/app/controllers/grades_controller.ts
@@ -3,7 +3,7 @@ import { inject } from '@adonisjs/core'
 import type { HttpContext } from '@adonisjs/core/http'
 import { DateTime } from 'luxon'
 
-const PERIODS = ['MONTH', 'SEMESTER', 'YEAR']
+const PERIODS = ['MONTH', 'TRIMESTER', 'YEAR']
 
 @inject()
 export default class GradesController {
@@ -37,5 +37,22 @@ export default class GradesController {
     return this.gradeService.getPeriodGrade(userId, startDate, months)
   }
 
-  // TODO: Radar chart for subjects
+  // GET /averages
+  async averages({ auth, request, response }: HttpContext) {
+    const period = request.input('period', PERIODS[0]).toUpperCase()
+    if (!PERIODS.includes(period)) {
+      return response.badRequest({
+        message: `Invalid period. Allowed values are: ${PERIODS.join(', ')}`,
+      })
+    }
+
+    const userId = auth.user!.id
+    if (period === PERIODS[0]) {
+      const startDate = DateTime.now().minus({ month: 1 })
+      return this.gradeService.getSubjectsAverages(userId, startDate, 1)
+    }
+    const months = period === PERIODS[1] ? 3 : 12
+    const startDate = DateTime.now().minus({ months })
+    return this.gradeService.getSubjectsAverages(userId, startDate, months)
+  }
 }
diff --git a/app/services/grade_service.ts b/app/services/grade_service.ts
index 84149e3..09b0b21 100644
--- a/app/services/grade_service.ts
+++ b/app/services/grade_service.ts
@@ -3,14 +3,16 @@ import { DateTime } from 'luxon'
 
 export class GradeService {
   private calculateAverage(colles: Colle[]) {
-    const total = colles.reduce((sum, colle) => sum + colle.grade, 0)
-    return parseFloat((total / colles.length).toFixed(2))
+    const total = colles
+      .map((colle) => parseFloat(colle.grade?.toString()))
+      .filter(Boolean)
+      .reduce((sum, grade) => sum + grade, 0)
+    return (total / colles.length).toFixed(2)
   }
 
   private calculateSubjectAverage(colles: Colle[], subject: string) {
-    const subjectColles = colles.filter((colle) => colle.subject.name === subject)
-    const total = subjectColles.reduce((sum, colle) => sum + colle.grade, 0)
-    return parseFloat((total / subjectColles.length).toFixed(2))
+    const subjectColles = colles.filter((colle) => colle.subject.name === subject && colle.grade)
+    return this.calculateAverage(subjectColles)
   }
 
   private getSubjects(colles: Colle[]) {
@@ -21,7 +23,22 @@ export class GradeService {
     return colles.filter((colle) => colle.date >= startDate && colle.date < endDate)
   }
 
-  private getColles(userId: number, startDate: DateTime, months: number = 0) {
+  public async getSubjectsAverages(userId: number, startDate: DateTime, months: number = 0) {
+    const colles = await this.getColles(userId, startDate, months)
+    const subjects = this.getSubjects(colles)
+    const subjectAverages: SubjectPerformance[] = []
+    for (const subject of subjects) {
+      const average = this.calculateSubjectAverage(colles, subject)
+      subjectAverages.push({ subject, average })
+    }
+    const globalAverage = this.calculateAverage(colles)
+    return {
+      globalAverage,
+      subjectAverages,
+    }
+  }
+
+  public getColles(userId: number, startDate: DateTime, months: number = 0) {
     const endDate = startDate.plus({ months })
     return Colle.query()
       .where('studentId', userId)
@@ -43,7 +60,7 @@ export class GradeService {
     const colles = await this.getColles(userId, startDate, 1)
     const subjects = this.getSubjects(colles)
 
-    const results: PeriodResult[] = []
+    const results: any = []
     let periodStartDate = startDate
 
     for (let week = 1; week <= 4; week++) {
@@ -77,14 +94,14 @@ export class GradeService {
     const colles = await this.getColles(userId, startDate, months)
     const subjects = this.getSubjects(colles)
 
-    const results: PeriodResult[] = []
+    const results: any = []
     let periodStartDate = startDate
 
     let index = 1
 
     while (periodStartDate < startDate.plus({ months })) {
       const periodEndDate = periodStartDate.endOf('month')
-      const periodColles = this.getPeriodColles(colles, periodStartDate, periodEndDate)
+      const periodColles = this.getPeriodColles(colles, startDate, periodEndDate)
 
       const periodAverage = this.calculateAverage(periodColles)
       const subjectAverages = await this.getSubjectAverages(
@@ -121,14 +138,17 @@ export class GradeService {
     subjects: string[],
     periodColles: Colle[],
     allColles: Colle[],
-    previousResults: PeriodResult[],
+    previousResults: Record<string, number>[],
     unitIndex: number,
     userId: number,
     periodStart: DateTime
   ) {
     const results = await Promise.all(
       subjects.map(async (subject) => {
-        if (periodColles.length > 0) {
+        const subjectColles = periodColles.filter(
+          (colle) => colle.subject.name === subject && colle.grade
+        )
+        if (subjectColles.length > 0) {
           return {
             subject,
             average: this.calculateSubjectAverage(periodColles, subject),
@@ -137,11 +157,9 @@ export class GradeService {
 
         // Try to use the previous unit's average
         if (unitIndex > 1) {
-          const prev = previousResults[unitIndex - 2].subjectAverages?.find(
-            (s) => s.subject === subject
-          )
+          const prev = previousResults[unitIndex - 2]?.[subject]
           if (prev) {
-            return { subject, average: prev.average }
+            return { subject, average: prev }
           }
         }
 
@@ -163,11 +181,5 @@ export class GradeService {
 
 interface SubjectPerformance {
   subject: string
-  average: number
-}
-
-interface PeriodResult {
-  period: string
-  average: number
-  subjectAverages: SubjectPerformance[]
+  average: string
 }
diff --git a/start/routes.ts b/start/routes.ts
index d63898d..abfc8b2 100644
--- a/start/routes.ts
+++ b/start/routes.ts
@@ -62,6 +62,7 @@ router
 
 const GradesController = () => import('#controllers/grades_controller')
 router.get('/grades', [GradesController, 'index']).use(middleware.auth())
+router.get('/averages', [GradesController, 'averages']).use(middleware.auth())
 
 const InternalsController = () => import('#controllers/internals_controller')
 router