How to change the hint size of TextInputLayout

In your styles.xml

<style name="TextLabel" parent="TextAppearance.Design.Hint">
    <item name="android:textSize">16sp</item>
</style>

And then in your layout file:

<android.support.design.widget.TextInputLayout
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:layout_marginLeft="@dimen/activity_horizontal_margin"
         android:layout_marginRight="@dimen/activity_horizontal_margin"
         android:layout_marginTop="12dp"
         app:hintTextAppearance="@style/TextLabel"
         android:minHeight="30dp">