diff --git a/data/src/main/java/com/moez/QKSMS/repository/MessageRepositoryImpl.kt b/data/src/main/java/com/moez/QKSMS/repository/MessageRepositoryImpl.kt
index 1eb62d23..b91846ce 100644
--- a/data/src/main/java/com/moez/QKSMS/repository/MessageRepositoryImpl.kt
+++ b/data/src/main/java/com/moez/QKSMS/repository/MessageRepositoryImpl.kt
@@ -66,8 +66,11 @@ import java.io.File
 import java.io.FileNotFoundException
 import java.io.FileOutputStream
 import java.io.IOException
+import java.util.*
+import java.util.concurrent.TimeUnit
 import javax.inject.Inject
 import javax.inject.Singleton
+import kotlin.collections.ArrayList
 import kotlin.math.sqrt
 
 @Singleton
@@ -724,4 +727,14 @@ class MessageRepositoryImpl @Inject constructor(
         }
     }
 
-}
\ No newline at end of file
+    override fun getOldMessageCounts(maxAgeDays: Int): Map<Long, Int> {
+        return Realm.getDefaultInstance().use { realm ->
+            realm.where(Message::class.java)
+                    .lessThan("date", now() - TimeUnit.DAYS.toMillis(maxAgeDays.toLong()))
+                    .findAll()
+                    .groupingBy { message -> message.threadId }
+                    .eachCount()
+        }
+    }
+
+}
diff --git a/domain/src/main/java/com/moez/QKSMS/repository/ConversationRepository.kt b/domain/src/main/java/com/moez/QKSMS/repository/ConversationRepository.kt
index 7ccf33ff..e94d1c9f 100644
--- a/domain/src/main/java/com/moez/QKSMS/repository/ConversationRepository.kt
+++ b/domain/src/main/java/com/moez/QKSMS/repository/ConversationRepository.kt
@@ -91,4 +91,4 @@ interface ConversationRepository {
 
     fun deleteConversations(vararg threadIds: Long)
 
-}
\ No newline at end of file
+}
diff --git a/domain/src/main/java/com/moez/QKSMS/repository/MessageRepository.kt b/domain/src/main/java/com/moez/QKSMS/repository/MessageRepository.kt
index 217e312a..ce09b206 100644
--- a/domain/src/main/java/com/moez/QKSMS/repository/MessageRepository.kt
+++ b/domain/src/main/java/com/moez/QKSMS/repository/MessageRepository.kt
@@ -102,4 +102,9 @@ interface MessageRepository {
 
     fun deleteMessages(vararg messageIds: Long)
 
+    /**
+     * Returns the number of messages older than [maxAgeDays] per conversation
+     */
+    fun getOldMessageCounts(maxAgeDays: Int): Map<Long, Int>
+
 }
diff --git a/presentation/src/main/java/com/moez/QKSMS/feature/settings/SettingsController.kt b/presentation/src/main/java/com/moez/QKSMS/feature/settings/SettingsController.kt
index eace81b3..104a305b 100644
--- a/presentation/src/main/java/com/moez/QKSMS/feature/settings/SettingsController.kt
+++ b/presentation/src/main/java/com/moez/QKSMS/feature/settings/SettingsController.kt
@@ -24,6 +24,7 @@ import android.content.Context
 import android.os.Build
 import android.text.format.DateFormat
 import android.view.View
+import androidx.appcompat.app.AlertDialog
 import androidx.core.view.isVisible
 import com.bluelinelabs.conductor.RouterTransaction
 import com.google.android.material.snackbar.Snackbar
@@ -39,9 +40,9 @@ import com.moez.QKSMS.common.util.Colors
 import com.moez.QKSMS.common.util.extensions.animateLayoutChanges
 import com.moez.QKSMS.common.util.extensions.setBackgroundTint
 import com.moez.QKSMS.common.util.extensions.setVisible
-import com.moez.QKSMS.common.widget.TextInputDialog
 import com.moez.QKSMS.common.widget.PreferenceView
 import com.moez.QKSMS.common.widget.QkSwitch
+import com.moez.QKSMS.common.widget.TextInputDialog
 import com.moez.QKSMS.databinding.SettingsControllerBinding
 import com.moez.QKSMS.feature.settings.about.AboutController
 import com.moez.QKSMS.feature.settings.autodelete.AutoDeleteDialog
@@ -55,7 +56,11 @@ import com.uber.autodispose.autoDisposable
 import io.reactivex.Observable
 import io.reactivex.subjects.PublishSubject
 import io.reactivex.subjects.Subject
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.suspendCancellableCoroutine
+import kotlinx.coroutines.withContext
 import javax.inject.Inject
+import kotlin.coroutines.resume
 
 class SettingsController : QkController<SettingsView, SettingsState, SettingsPresenter, SettingsControllerBinding>(
         SettingsControllerBinding::inflate
@@ -192,7 +197,8 @@ class SettingsController : QkController<SettingsView, SettingsState, SettingsPre
             is SyncRepository.SyncProgress.Running -> {
                 binding.syncingProgress.isVisible = true
                 binding.syncingProgress.max = state.syncProgress.max
-                progressAnimator.apply { setIntValues(binding.syncingProgress.progress, state.syncProgress.progress) }.start()
+                progressAnimator.apply { setIntValues(binding.syncingProgress.progress, state.syncProgress.progress) }
+                        .start()
                 binding.syncingProgress.isIndeterminate = state.syncProgress.indeterminate
             }
         }
@@ -231,6 +237,17 @@ class SettingsController : QkController<SettingsView, SettingsState, SettingsPre
 
     override fun showAutoDeleteDialog(days: Int) = autoDeleteDialog.setExpiry(days).show()
 
+    override suspend fun showAutoDeleteWarningDialog(messages: Int): Boolean = withContext(Dispatchers.Main) {
+        suspendCancellableCoroutine<Boolean> { cont ->
+            AlertDialog.Builder(activity!!)
+                    .setMessage(context.resources.getString(R.string.settings_auto_delete_warning, messages))
+                    .setOnCancelListener { cont.resume(false) }
+                    .setNegativeButton(R.string.button_cancel) { _, _ -> cont.resume(false) }
+                    .setPositiveButton(R.string.button_yes) { _, _ -> cont.resume(true) }
+                    .show()
+        }
+    }
+
     override fun showMmsSizePicker() = mmsSizeDialog.show(activity!!)
 
     override fun showSwipeActions() {
diff --git a/presentation/src/main/java/com/moez/QKSMS/feature/settings/SettingsPresenter.kt b/presentation/src/main/java/com/moez/QKSMS/feature/settings/SettingsPresenter.kt
index 17923df9..708d0671 100644
--- a/presentation/src/main/java/com/moez/QKSMS/feature/settings/SettingsPresenter.kt
+++ b/presentation/src/main/java/com/moez/QKSMS/feature/settings/SettingsPresenter.kt
@@ -28,6 +28,7 @@ import com.moez.QKSMS.common.util.DateFormatter
 import com.moez.QKSMS.common.util.extensions.makeToast
 import com.moez.QKSMS.interactor.SyncMessages
 import com.moez.QKSMS.manager.AnalyticsManager
+import com.moez.QKSMS.repository.MessageRepository
 import com.moez.QKSMS.repository.SyncRepository
 import com.moez.QKSMS.util.NightModeManager
 import com.moez.QKSMS.util.Preferences
@@ -35,6 +36,8 @@ import com.uber.autodispose.android.lifecycle.scope
 import com.uber.autodispose.autoDisposable
 import io.reactivex.rxkotlin.plusAssign
 import io.reactivex.rxkotlin.withLatestFrom
+import io.reactivex.schedulers.Schedulers
+import kotlinx.coroutines.runBlocking
 import timber.log.Timber
 import java.util.*
 import java.util.concurrent.TimeUnit
@@ -47,6 +50,7 @@ class SettingsPresenter @Inject constructor(
     private val context: Context,
     private val billingManager: BillingManager,
     private val dateFormatter: DateFormatter,
+    private val messageRepo: MessageRepository,
     private val navigator: Navigator,
     private val nightModeManager: NightModeManager,
     private val prefs: Preferences,
@@ -253,6 +257,15 @@ class SettingsPresenter @Inject constructor(
                 .subscribe()
 
         view.autoDeleteChanged()
+                .observeOn(Schedulers.io())
+                .filter { maxAge ->
+                    if (maxAge == 0) {
+                        return@filter true
+                    }
+
+                    val counts = messageRepo.getOldMessageCounts(maxAge)
+                    runBlocking { view.showAutoDeleteWarningDialog(counts.values.sum()) }
+                }
                 .doOnNext(prefs.autoDelete::set)
                 .autoDisposable(view.scope())
                 .subscribe()
diff --git a/presentation/src/main/java/com/moez/QKSMS/feature/settings/SettingsView.kt b/presentation/src/main/java/com/moez/QKSMS/feature/settings/SettingsView.kt
index f0350609..853b23d6 100644
--- a/presentation/src/main/java/com/moez/QKSMS/feature/settings/SettingsView.kt
+++ b/presentation/src/main/java/com/moez/QKSMS/feature/settings/SettingsView.kt
@@ -43,6 +43,7 @@ interface SettingsView : QkViewContract<SettingsState> {
     fun showDelayDurationDialog()
     fun showSignatureDialog(signature: String)
     fun showAutoDeleteDialog(days: Int)
+    suspend fun showAutoDeleteWarningDialog(messages: Int): Boolean
     fun showMmsSizePicker()
     fun showSwipeActions()
     fun showThemePicker()
diff --git a/presentation/src/main/res/values/strings.xml b/presentation/src/main/res/values/strings.xml
index 09dc8371..50f4752a 100644
--- a/presentation/src/main/res/values/strings.xml
+++ b/presentation/src/main/res/values/strings.xml
@@ -262,6 +262,7 @@
     <string name="settings_auto_delete_dialog_message">Messages will be deleted after the specified number of days</string>
     <string name="settings_auto_delete_dialog_hint">Number of days</string>
     <string name="settings_auto_delete_never">Never</string>
+    <string name="settings_auto_delete_warning">Are you sure you would like to enable this setting? %1$d messages will be deleted</string>
     <plurals name="settings_auto_delete_summary">
         <item quantity="zero">Never</item>
         <item quantity="one">After 1 day</item>