Wiktionary
ballpark figure
n. (context chiefly US idiomatic English) An educated guess or estimation within acceptable bounds.
Usage examples of "ballpark figure".
It does happen: in an informal survey of major league clubs, I came up with a ballpark figure (grin) of three or four serious injuries to fans caused by batted balls per club, per year.
I could have at least given him a ballpark figure, but the question had never come up and I'd been too busy trying to evaluate his status for my report to Donovan.
That should add between eight hundred and a thousand dollars a week to you and your crew, ballpark figure.
As a ballpark figure, my regiment is holding three times as much line as I was taught was the absolute maximum at Leavenworth, (Graduation from the U.