If it's too big, you can use adhesive foam tape on the inside of the crown to create a snugger fit.

Do you have a you're watching so I can give you the exact measurements? Let's make a tiny paper cowboy hat! | Karagamii Archive

Are you using a or starting from a blank sheet ? Is this for a costume or a miniature decoration ?

Fold up small "tabs" inside the center hole to provide a surface for gluing. 3. Attach and Shape

Trace and cut a large oval out of a separate sheet of paper.