off the top of one's head

off the top of (one's) head

From memory or without much or careful consideration. A: "How much can we expect to earn this quarter?" B: "Off the top of my head, it should be around $200,000, but I'll have to check the figures when I get to the office." I know of two people who are coming off the top of my head, but I'm pretty sure more said they'd be here. John can list the capital cities of all 50 states off the top of his head.
See also: head, of, off, top
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

off the top of one's head

In an impromptu way, without much thought, as in Off the top of my head I'd say we'll double our profits in a year. This idiom suggests one has not used the inside of one's head before making some statement. [Mid-1900s]
See also: head, of, off, top
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

off the top of one's head

Extemporaneously, impromptu; impetuously. A mid-twentieth-century Americanism, the term appeared in Harold L. Ickes’s Secret Diary (1939): “He was impetuous and inclined to think off the top of his head at times.” Author June Drummond (Junta, 1989) wrote: “‘And then, you just acted off the top of your head.’ Richard half-smiled. ‘You know I have that failing.’”
See also: head, of, off, top
The Dictionary of Clichés by Christine Ammer Copyright © 2013 by Christine Ammer
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References in periodicals archive ?
Artistry can also come right off the top of one's head. The way Joe Morgan analyzes baseball on TV.