Most ornaments do not have a measurement on the outside of the box and it is very hard to get a good measurement. The easiest way IMO is to use a wooden chopstick or wooden skewer and a pen. Insert the skewer into the ball and mark at the top. Then pull the skewer out and reinsert just until the tip of the skewer hits were the insert would start and mark the skewer again at the top. Your ornament measurement will be the length of skewer between your two marks. Make sense? You may want to make a test sheet with two or three different size circles (usually the difference is is within 1/4 inch) to get it right. I like my ornaments to be a hair bigger than the inside of the ball to that they "fit" and don't shift. HTH!
Rose
mom 2 Katie (almost 3!)
& Jack (19 months)