Change the size of a toolbar button or drop-down list box

On the Tools menu, click Customize.
Make sure the toolbar you want to change is visible.
How?
1. In the Customize dialog box, click the Toolbars tab.
2. Select the check box for the toolbar you want to display.
With the Customize dialog box open, click the list box you want to change— for example, the Font or Font Size box on the Formatting toolbar.
Point to the left or right edge of the box. When the pointer changes to a double-headed arrow, drag the edge of the box to change its width.