Q. Is it acceptable to hyphenate an approximate measurement? Here are some examples: “I boxed up two-hundred-something widgets.” “It will take five-or-so days to complete.” “I need two-and-a-half months for a project of that scope.” (A half month is not a specific number of days.) Thank you for your help!
A. Hyphenation isn’t normally related to how exact a measurement might be. In your three examples, we’d apply no hyphens but one en dash (for the widgets):
I boxed up two hundred–something widgets.
It will take five or so days to complete.
I need two and a half months for a project of that scope.
According to Merriam-Webster, the word something in the sense you’ve used it—“some indeterminate amount more than a specified number”—is a combining form that connects to other words with a hyphen, as in “twenty-something years old.” When joined to the open compound “two hundred,” it gets an en dash in Chicago style (see CMOS 6.86). The other expressions of approximation in the examples above—“or so” and “and a half”—are ordinary phrases that don’t require hyphens.