diff --git a/app/src/main/java/com/github/axet/audiorecorder/activities/MainActivity.java b/app/src/main/java/com/github/axet/audiorecorder/activities/MainActivity.java
index 6cb27f7..3dc8d8b 100644
--- a/app/src/main/java/com/github/axet/audiorecorder/activities/MainActivity.java
+++ b/app/src/main/java/com/github/axet/audiorecorder/activities/MainActivity.java
@@ -517,6 +517,7 @@ public class MainActivity extends AppCompatActivity implements AbsListView.OnScr
     @Override
     protected void onResume() {
         super.onResume();
+        Log.d(TAG, "onResume");
 
         if (permitted(PERMISSIONS))
             load();
@@ -525,6 +526,8 @@ public class MainActivity extends AppCompatActivity implements AbsListView.OnScr
 
         checkPending();
 
+        updateHeader();
+
         final int selected = getLastRecording();
         list.setSelection(selected);
         if (selected != -1) {
@@ -659,4 +662,34 @@ public class MainActivity extends AppCompatActivity implements AbsListView.OnScr
         AppIndex.AppIndexApi.end(client, viewAction);
         client.disconnect();
     }
+
+    void updateHeader() {
+        File f = storage.getTempRecording();
+        long free = storage.getFree(f);
+
+        long sec = storage.average(free);
+
+        String str = "";
+
+        long diff = sec;
+        int diffSeconds = (int) (diff / 1000 % 60);
+        int diffMinutes = (int) (diff / (60 * 1000) % 60);
+        int diffHours = (int) (diff / (60 * 60 * 1000) % 24);
+        int diffDays = (int) (diff / (24 * 60 * 60 * 1000));
+
+        if (diffDays > 0) {
+            str = getResources().getQuantityString(R.plurals.days, diffDays, diffDays);
+        } else if (diffHours > 0) {
+            str = getResources().getQuantityString(R.plurals.hours, diffHours, diffHours);
+        } else if (diffMinutes > 0) {
+            str = getResources().getQuantityString(R.plurals.minutes, diffMinutes, diffMinutes);
+        } else if (diffSeconds > 0) {
+            str = getResources().getQuantityString(R.plurals.seconds, diffSeconds, diffSeconds);
+        }
+
+        String ss = String.format("free %s ~ %s left", MainApplication.formatSize(free), str);
+
+        TextView text = (TextView) findViewById(R.id.space_left);
+        text.setText(ss);
+    }
 }
diff --git a/app/src/main/java/com/github/axet/audiorecorder/app/MainApplication.java b/app/src/main/java/com/github/axet/audiorecorder/app/MainApplication.java
index a3e38c5..d129889 100644
--- a/app/src/main/java/com/github/axet/audiorecorder/app/MainApplication.java
+++ b/app/src/main/java/com/github/axet/audiorecorder/app/MainApplication.java
@@ -26,7 +26,10 @@ public class MainApplication extends Application {
     }
 
     public static String formatSize(long s) {
-        if (s > 0.1 * 1024 * 1024) {
+        if (s > 0.1 * 1024 * 1024 * 1024) {
+            float f = s / 1024f / 1024f / 1024f;
+            return String.format("%.1f GB", f);
+        } else if (s > 0.1 * 1024 * 1024) {
             float f = s / 1024f / 1024f;
             return String.format("%.1f MB", f);
         } else {
diff --git a/app/src/main/java/com/github/axet/audiorecorder/app/Storage.java b/app/src/main/java/com/github/axet/audiorecorder/app/Storage.java
index 6773f33..6d51de6 100644
--- a/app/src/main/java/com/github/axet/audiorecorder/app/Storage.java
+++ b/app/src/main/java/com/github/axet/audiorecorder/app/Storage.java
@@ -5,11 +5,18 @@ import android.content.ContentResolver;
 import android.content.Context;
 import android.content.SharedPreferences;
 import android.content.pm.PackageManager;
+import android.media.AudioFormat;
+import android.os.Build;
+import android.os.StatFs;
 import android.preference.PreferenceManager;
 import android.support.v4.content.ContextCompat;
+import android.util.Log;
 import android.widget.Toast;
 
 import com.github.axet.audiorecorder.R;
+import com.github.axet.audiorecorder.activities.RecordingActivity;
+import com.github.axet.audiorecorder.encoders.FormatM4A;
+import com.github.axet.audiorecorder.encoders.FormatWAV;
 
 import java.io.File;
 import java.io.FileInputStream;
@@ -185,8 +192,68 @@ public class Storage {
         return list;
     }
 
+    // get average recording miliseconds based on compression format
+    public long average(long free) {
+        final SharedPreferences shared = PreferenceManager.getDefaultSharedPreferences(context);
+        int rate = Integer.parseInt(shared.getString(MainApplication.PREFERENCE_RATE, ""));
+        String ext = shared.getString(MainApplication.PREFERENCE_ENCODING, "");
+
+        if (ext.equals("m4a")) {
+            long y1 = 365723; // one minute sample 16000Hz
+            long x1 = 16000; // at 16000
+            long y2 = 493743; // one minute sample
+            long x2 = 44000; // at 44000
+            long x = rate;
+            long y = (x - x1) * (y2 - y1) / (x2 - x1) + y1;
+
+            int m = RawSamples.CHANNEL_CONFIG == AudioFormat.CHANNEL_IN_MONO ? 1 : 2;
+            long perSec = (y / 60) * m;
+            return free / perSec * 1000;
+        }
+
+        // default raw
+        int m = RawSamples.CHANNEL_CONFIG == AudioFormat.CHANNEL_IN_MONO ? 1 : 2;
+        int c = RawSamples.AUDIO_FORMAT == AudioFormat.ENCODING_PCM_16BIT ? 2 : 1;
+        long perSec = (c * m * rate);
+        return free / perSec * 1000;
+    }
+
+    public long getFree(File f) {
+        while (!f.exists())
+            f = f.getParentFile();
+
+        StatFs fsi = new StatFs(f.getPath());
+        if (Build.VERSION.SDK_INT < 18)
+            return fsi.getBlockSize() * fsi.getAvailableBlocks();
+        else
+            return fsi.getBlockSizeLong() * fsi.getAvailableBlocksLong();
+    }
+
     public File getTempRecording() {
-        return new File(context.getApplicationInfo().dataDir, TMP_REC);
+        File internal = new File(context.getApplicationInfo().dataDir, TMP_REC);
+
+        // Starting in KITKAT, no permissions are required to read or write to the returned path;
+        // it's always accessible to the calling app
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT) {
+            if (!permitted(PERMISSIONS))
+                return internal;
+        }
+
+        File external = new File(context.getExternalCacheDir(), TMP_REC);
+
+        if (internal.exists())
+            return internal;
+
+        if (external.exists())
+            return external;
+
+        long freeI = getFree(internal);
+        long freeE = getFree(external);
+
+        if (freeI > freeE)
+            return internal;
+        else
+            return external;
     }
 
     public FileOutputStream open(File f) {
diff --git a/app/src/main/res/layout/content_main.xml b/app/src/main/res/layout/content_main.xml
index 0144341..2b94ac4 100644
--- a/app/src/main/res/layout/content_main.xml
+++ b/app/src/main/res/layout/content_main.xml
@@ -1,17 +1,25 @@
 <?xml version="1.0" encoding="utf-8"?>
-<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
+    android:orientation="vertical"
     android:paddingBottom="@dimen/activity_vertical_margin"
     android:paddingLeft="@dimen/activity_horizontal_margin"
     android:paddingRight="@dimen/activity_horizontal_margin"
-    android:paddingTop="@dimen/activity_vertical_margin"
     app:layout_behavior="@string/appbar_scrolling_view_behavior"
     tools:context=".activities.MainActivity"
     tools:showIn="@layout/activity_main">
 
+    <TextView
+        android:id="@+id/space_left"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:padding="5dp"
+        android:text="free 32G ~ 3 hours left" />
+
     <ListView
         android:id="@+id/list"
         android:layout_width="match_parent"
@@ -27,4 +35,4 @@
         android:textAlignment="center"
         android:visibility="gone"></TextView>
 
-</FrameLayout>
+</LinearLayout>
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 2aa6034..b15321d 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -33,4 +33,25 @@
 
     <string name="title_activity_main">Audio Recorder</string>
     <string name="action_settings">Settings</string>
+
+    <plurals name="days">
+        <item quantity="one">%d day</item>
+        <item quantity="other">%d days</item>
+    </plurals>
+
+    <plurals name="hours">
+        <item quantity="one">%d hour</item>
+        <item quantity="other">%d hours</item>
+    </plurals>
+
+    <plurals name="minutes">
+        <item quantity="one">%d minute</item>
+        <item quantity="other">%d minutes</item>
+    </plurals>
+
+    <plurals name="seconds">
+        <item quantity="one">%d second</item>
+        <item quantity="other">%d seconds</item>
+    </plurals>
+
 </resources>