diff --git a/app/src/main/java/io/github/wulkanowy/data/repositories/PreferencesRepository.kt b/app/src/main/java/io/github/wulkanowy/data/repositories/PreferencesRepository.kt
index 430a6cac..205baa3a 100644
--- a/app/src/main/java/io/github/wulkanowy/data/repositories/PreferencesRepository.kt
+++ b/app/src/main/java/io/github/wulkanowy/data/repositories/PreferencesRepository.kt
@@ -24,8 +24,11 @@ class PreferencesRepository @Inject constructor(
     val currentTheme: Int
         get() = sharedPref.getString(currentThemeKey, "1")?.toInt() ?: 1
 
-    val gradeModifier: Double
-        get() = sharedPref.getString(context.getString(R.string.pref_key_grade_modifier), "0.0")?.toDouble() ?: 0.0
+    val gradePlusModifier: Double
+        get() = sharedPref.getString(context.getString(R.string.pref_key_grade_modifier_plus), "0.0")?.toDouble() ?: 0.0
+
+    val gradeMinusModifier: Double
+        get() = sharedPref.getString(context.getString(R.string.pref_key_grade_modifier_minus), "0.0")?.toDouble() ?: 0.0
 
     val serviceEnablesKey: String = context.getString(R.string.pref_key_services_enable)
     val isServiceEnabled: Boolean
diff --git a/app/src/main/java/io/github/wulkanowy/ui/modules/grade/details/GradeDetailsPresenter.kt b/app/src/main/java/io/github/wulkanowy/ui/modules/grade/details/GradeDetailsPresenter.kt
index c17c2402..241b9f68 100644
--- a/app/src/main/java/io/github/wulkanowy/ui/modules/grade/details/GradeDetailsPresenter.kt
+++ b/app/src/main/java/io/github/wulkanowy/ui/modules/grade/details/GradeDetailsPresenter.kt
@@ -34,7 +34,7 @@ class GradeDetailsPresenter @Inject constructor(
         disposable.add(studentRepository.getCurrentStudent()
             .flatMap { semesterRepository.getSemesters(it) }
             .flatMap { gradeRepository.getGrades(it.first { item -> item.semesterId == semesterId }, forceRefresh) }
-            .map { it.map { item -> item.changeModifier(preferencesRepository.gradeModifier) } }
+            .map { it.map { item -> item.changeModifier(preferencesRepository.gradePlusModifier, preferencesRepository.gradeMinusModifier) } }
             .map { createGradeItems(it.groupBy { grade -> grade.subject }.toSortedMap()) }
             .subscribeOn(schedulers.backgroundThread)
             .observeOn(schedulers.mainThread)
diff --git a/app/src/main/java/io/github/wulkanowy/ui/modules/grade/summary/GradeSummaryPresenter.kt b/app/src/main/java/io/github/wulkanowy/ui/modules/grade/summary/GradeSummaryPresenter.kt
index f844995e..2715aac4 100644
--- a/app/src/main/java/io/github/wulkanowy/ui/modules/grade/summary/GradeSummaryPresenter.kt
+++ b/app/src/main/java/io/github/wulkanowy/ui/modules/grade/summary/GradeSummaryPresenter.kt
@@ -40,7 +40,7 @@ class GradeSummaryPresenter @Inject constructor(
                     .flatMap { gradesSummary ->
                         gradeRepository.getGrades(it, forceRefresh)
                             .map { grades ->
-                                grades.map { item -> item.changeModifier(preferencesRepository.gradeModifier) }
+                                grades.map { item -> item.changeModifier(preferencesRepository.gradePlusModifier, preferencesRepository.gradeMinusModifier) }
                                     .groupBy { grade -> grade.subject }
                                     .mapValues { entry -> entry.value.calcAverage() }
                                     .filterValues { value -> value != 0.0 }
diff --git a/app/src/main/java/io/github/wulkanowy/utils/GradeExtension.kt b/app/src/main/java/io/github/wulkanowy/utils/GradeExtension.kt
index b75cca1a..638bf364 100644
--- a/app/src/main/java/io/github/wulkanowy/utils/GradeExtension.kt
+++ b/app/src/main/java/io/github/wulkanowy/utils/GradeExtension.kt
@@ -47,9 +47,14 @@ inline val Grade.colorStringId: Int
         }
     }
 
-fun Grade.changeModifier(newModifier: Double): Grade {
-    if (modifier != 0.0 && newModifier != 0.0) {
-        modifier = if (modifier > 0) newModifier else -newModifier
+fun Grade.changeModifier(plusModifier: Double, minusModifier: Double): Grade {
+    if (modifier != 0.0) {
+        if (plusModifier != 0.0 && modifier > 0) {
+            modifier = plusModifier
+        }
+        if (minusModifier != .0 && modifier < 0) {
+            modifier = -minusModifier
+        }
     }
     return this
-}
\ No newline at end of file
+}
diff --git a/app/src/main/res/values-pl/strings.xml b/app/src/main/res/values-pl/strings.xml
index 79a51e2a..1fd97160 100644
--- a/app/src/main/res/values-pl/strings.xml
+++ b/app/src/main/res/values-pl/strings.xml
@@ -217,7 +217,8 @@
     <string name="pref_view_summary">Pokazuj podsumowanie w ocenach</string>
     <string name="pref_view_present">Pokazuj obecność we frekwencji</string>
     <string name="pref_view_theme_dark">Ciemny motyw (Beta)</string>
-    <string name="pref_view_grade_modifier">Wartość plusa i minusa</string>
+    <string name="pref_view_grade_modifier_plus">Wartość plusa</string>
+    <string name="pref_view_grade_modifier_minus">Wartość minusa</string>
     <string name="pref_view_expand_grade">Rozwiń oceny</string>
 
     <string name="pref_notify_header">Powiadomienia</string>
diff --git a/app/src/main/res/values/preferences_keys.xml b/app/src/main/res/values/preferences_keys.xml
index cd0a9a65..ea2585e7 100644
--- a/app/src/main/res/values/preferences_keys.xml
+++ b/app/src/main/res/values/preferences_keys.xml
@@ -3,7 +3,8 @@
     <string name="pref_key_start_menu">start_menu</string>
     <string name="pref_key_attendance_present">attendance_present</string>
     <string name="pref_key_theme">theme</string>
-    <string name="pref_key_grade_modifier">grade_modifier</string>
+    <string name="pref_key_grade_modifier_plus">grade_modifier_plus</string>
+    <string name="pref_key_grade_modifier_minus">grade_modifier_minus</string>
     <string name="pref_key_expand_grade">expand_grade</string>
     <string name="pref_key_services_enable">services_enable</string>
     <string name="pref_key_services_interval">services_interval</string>
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 201d311a..fb955f3b 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -199,7 +199,8 @@
     <string name="pref_view_summary">Show the summary in the grades</string>
     <string name="pref_view_present">Show presence in attendance</string>
     <string name="pref_view_theme_dark">Dark theme (Beta)</string>
-    <string name="pref_view_grade_modifier">Value of the plus and minus</string>
+    <string name="pref_view_grade_modifier_plus">Value of the plus</string>
+    <string name="pref_view_grade_modifier_minus">Value of the minus</string>
     <string name="pref_view_expand_grade">Expand grades</string>
 
     <string name="pref_notify_header">Notifications</string>
diff --git a/app/src/main/res/xml/scheme_preferences.xml b/app/src/main/res/xml/scheme_preferences.xml
index 27addc83..1ba8885a 100644
--- a/app/src/main/res/xml/scheme_preferences.xml
+++ b/app/src/main/res/xml/scheme_preferences.xml
@@ -34,9 +34,17 @@
             android:defaultValue="0.0"
             android:entries="@array/grade_modifier_entries"
             android:entryValues="@array/grade_modifier_value"
-            android:key="@string/pref_key_grade_modifier"
+            android:key="@string/pref_key_grade_modifier_plus"
             android:summary="%s"
-            android:title="@string/pref_view_grade_modifier"
+            android:title="@string/pref_view_grade_modifier_plus"
+            app:iconSpaceReserved="false" />
+        <ListPreference
+            android:defaultValue="0.0"
+            android:entries="@array/grade_modifier_entries"
+            android:entryValues="@array/grade_modifier_value"
+            android:key="@string/pref_key_grade_modifier_minus"
+            android:summary="%s"
+            android:title="@string/pref_view_grade_modifier_minus"
             app:iconSpaceReserved="false" />
     </PreferenceCategory>
     <PreferenceCategory
diff --git a/app/src/test/java/io/github/wulkanowy/utils/GradeExtensionTest.kt b/app/src/test/java/io/github/wulkanowy/utils/GradeExtensionTest.kt
index 37f4dc4b..12a086ed 100644
--- a/app/src/test/java/io/github/wulkanowy/utils/GradeExtensionTest.kt
+++ b/app/src/test/java/io/github/wulkanowy/utils/GradeExtensionTest.kt
@@ -3,31 +3,30 @@ package io.github.wulkanowy.utils
 import io.github.wulkanowy.data.db.entities.Grade
 import io.github.wulkanowy.data.db.entities.GradeSummary
 import org.junit.Assert.assertEquals
+import org.junit.Before
 import org.junit.Test
-import org.mockito.Mockito.mock
+import org.mockito.Mock
+import org.mockito.MockitoAnnotations
 import org.threeten.bp.LocalDate
 
 class GradeExtensionTest {
 
+    @Mock
+    lateinit var date: LocalDate
+
+    @Before
+    fun before() {
+        MockitoAnnotations.initMocks(this)
+    }
+
     @Test
     fun calcWeightedAverage() {
-        val localDate = mock(LocalDate::class.java)
         assertEquals(3.47, listOf(
-            Grade(1, 1, "", "", 5, 0.33
-                , "", "", "", "", "",
-                6, localDate, ""),
-            Grade(1, 1, "", "", 5, -0.33
-                , "", "", "", "", "",
-                5, localDate, ""),
-            Grade(1, 1, "", "", 4, 0.0
-                , "", "", "", "", "",
-                1, localDate, ""),
-            Grade(1, 1, "", "", 1, 0.5
-                , "", "", "", "", "",
-                9, localDate, ""),
-            Grade(1, 1, "", "", 0, 0.0
-                , "", "", "", "", "",
-                0, localDate, "")
+            createGrade(5, 6, 0.33),
+            createGrade(5, 5, -0.33),
+            createGrade(4, 1, 0.0),
+            createGrade(1, 9, 0.5),
+            createGrade(0, 0, 0.0)
         ).calcAverage(), 0.005)
     }
 
@@ -42,16 +41,39 @@ class GradeExtensionTest {
     }
 
     @Test
-    fun changeModifierTest() {
-        val localDate = mock(LocalDate::class.java)
-        assertEquals(0.33, Grade(1, 1, "", "", 5, 0.25
-            , "", "", "", "", "",
-            6, localDate, "").changeModifier(0.33).modifier, 0.0)
-        assertEquals(-0.33, Grade(1, 1, "", "", 5, -0.25
-            , "", "", "", "", "",
-            6, localDate, "").changeModifier(0.33).modifier, 0.0)
-        assertEquals(0.25, Grade(1, 1, "", "", 5, 0.25
-            , "", "", "", "", "",
-            6, localDate, "").changeModifier(0.0).modifier, 0.0)
+    fun changeModifier_default() {
+        assertEquals(.33, createGrade(5, 0, .33).changeModifier(.0, .0).modifier, .0)
+        assertEquals(-.33, createGrade(5, 0, -.33).changeModifier(.0, .0).modifier, .0)
+    }
+
+    @Test
+    fun changeModifier_plus() {
+        assertEquals(.33, createGrade(5, 0, .25).changeModifier(.33, .50).modifier, .0)
+        assertEquals(.25, createGrade(5, 0, .33).changeModifier(.25, .0).modifier, .0)
+    }
+
+    @Test
+    fun changeModifier_minus() {
+        assertEquals(-.33, createGrade(5, 0, -.25).changeModifier(.25, .33).modifier, .0)
+        assertEquals(-.25, createGrade(5, 0, -.33).changeModifier(.0, .25).modifier, .0)
+    }
+
+    private fun createGrade(value: Int, weightValue: Int = 0, modifier: Double = 0.25): Grade {
+        return Grade(
+            semesterId = 1,
+            studentId = 1,
+            subject = "",
+            entry = "",
+            value = value,
+            modifier = modifier,
+            comment = "",
+            color = "",
+            gradeSymbol = "",
+            description = "",
+            weight = "",
+            weightValue = weightValue,
+            date = date,
+            teacher = ""
+        )
     }
 }