<resources>

    <!-- Default screen margins, per the Android Design guidelines. -->

    <dimen name="btn_width">16dp</dimen>

    <dimen name="btn_height">16dp</dimen>

</resources>

<Button

android:text="@string/test_dimen1"

android:id="@+id/Button01"

android:layout_width="@dimen/btn_width"

android:layout_height="@dimen/btn_height"/>