Is there a way to figure out the dimensions of the U.S. flag without unfolding it?

I am looking for a triangular display case and I do not know the dimensions of the flag because it is folded. The flag was presented at a funeral with military honors. Is there a way to maybe measure from point to point on the stars that are visible or some other means, or is there a standard size that is used? I am uming that it should be 5 x 9 but I want to make sure. Thanks in advance.