The New York Public Library’s revised renovation plan — to upgrade the Mid-Manhattan Library and create more public space in its flagship Fifth Avenue building — is expected to cost about $300 million, according to library officials who outlined new details of the project in interviews.

The anticipated budget matches what the library had originally suggested its previous plan — to insert a circulating branch at its main library at 42nd Street — might cost.

But officials, for the first time, revealed that the original plan, mostly scrapped last month in large part because of questions about the price tag, would actually have cost more than $500 million, according to independent estimates they commissioned last June.