Estimate vs. Guess

By Mark Nichol

What’s the difference between estimate and guess? The distinction between the two words is one of the degree of care taken in arriving at a conclusion.

Estimate is from the Latin word aestimare, meaning “to value.” That term is also the origin of estimable, which means “capable of being estimated” or “worthy of esteem” (but is more often used in the latter sense), and of esteem, which means “regard” (and is usually associated with high regard).

To estimate is to judge the extent, nature, or value of something, with the implication that the result is based on expertise or familiarity. An estimate is the resulting calculation or judgment. (A related term is approximation, meaning “close or near.”)

Bridging the gap between a guess and an estimate is an educated guess, a more casual estimate. An idiomatic term for this type of middle-ground conclusion is “ballpark figure.” The origin of this American English idiom, which alludes to a baseball stadium, is not certain, but one conclusion is that it is related to “in the ballpark,” meaning “close” in the sense that one at such a location may not be in a precise location but is in the stadium.

To guess is to believe or suppose, to form an opinion based on little or no evidence, or to be correct by chance or conjecture. A guess is a thought or idea arrived at by one of these methods. Synonyms for guess include conjecture and surmise, which like guess can be employed both as verbs and as nouns.

One might also have a hunch or an intuition, or may engage in guesswork or speculation. “Dead reckoning” means the same thing as guesswork, though it originally referred to navigation based on reliable information. Near synonyms describing thoughts or ideas developed with more rigor include hypothesis and supposition, as well as theory and thesis.

In summary, a guess is a casual, perhaps spontaneous conclusion, whereas an estimate is based on some thought and/or data.

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10 Responses to “Estimate vs. Guess”

  • thebluebird11

    You know, it’s interesting to come back to the archives after a while and see what else has been posted.
    @Mark: Now that you mention another meaning of “swag,” I think I vaguely remember hearing it used that way (logofied freebies), or something similar. Or maybe it had the connotation of “bling,” i.e. lots of shiny stuff, expensive jewelry or whatever. In fact, I just got back from, and I haven’t laughed so hard in a while, their definitions of SWAG (as a word and as an acronym). If anybody is still here reading this archived post, I suggest you check it out, if for nothing else than a good laugh!

  • Jevon

    I like this definition. Although, if someone told me they made an educated guess, I would still not take them too seriously.

  • David

    Dead reckoning is actually De’d reckoning, which is short for deduced reckoning. I doubt any navigator got anywhere reliable based on guesswork, and considering your definition of a guess, dead reckoning is decidedly dissimilar even in today’s usage. Hence, I think a more accurate explanation would be that the term is similar to deduction, not ‘guesswork’. In the old days, navigators deduced their position based on instruments and tools considered accurate and reliable.

  • Stephen

    The difference between ‘guess’ and ‘estimate’ is purely one of connotation. There’s no difference in the dictionary definition.

    However, ‘theory’, ‘hypothesis’ and ‘thesis’ all have specific scientific definitions. A theory is not just an idea developed with rigour, but one that has been thoroughly tested and validated. From the American Association for the Advancement of Science via Wikipedia:

    “A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment. Such fact-supported theories are not “guesses” but reliable accounts of the real world. The theory of biological evolution is more than “just a theory.” It is as factual an explanation of the universe as the atomic theory of matter or the germ theory of disease. Our understanding of gravity is still a work in progress. But the phenomenon of gravity, like evolution, is an accepted fact.”

  • Sally

    Nicely put, AnWulf! We like to *think* estimates are more considered than guesses, but…

    Here in Australia we have ‘guesstimate,’ which is a particularly useful term, especially in politics.

    (Stop me before I start quoting Churchill about “lies, damned lies and statistics” and “never believe a statistic you haven’t falsified yourself.”)

  • AnWulf

    You’re all wet on this one. A guess can be anything from a wild conjecture to well-calculated number … the same goes for an estimate.

    From the Oxford American Writer’s Thesaurus:

    estimate the cost: calculate roughly, approximate, *guess*

    he guessed she was about 40: *estimate*, hazard a guess, reckon, gauge, judge, calculate; hypothesize, postulate, predict, speculate, conjecture, surmise; informal guesstimate.

  • Mark Nichol


    My guess is that the term your daughter is familiar with is a rap-slang back-formation of swagger. But swag also means “complimentary promotional items,” such as T-shirts, key chains, refrigerator magnets, and other logo-bedecked items, or the kind of products handed out in goodie bags at the Oscars and like events. (The term is sometimes pronounced “schwag.”)

  • thebluebird11

    @Ed: Ha, that would explain why, when I was playing “Draw Something” with my daughter, and the word I got was “swag,” and I drew a chandelier with a chain swag (and an arrow pointing to the chain), she didn’t know what I was talking about. When I told her it was a swag, she said that’s not what swag means! LOL
    In a somewhat related vein (only because it’s an acronym), I have a little hand-held electronic solitaire game, and every time I am “shut out,” I consider it a TWOT. If you say that out loud to someone, they think you’re being rude (or bizarre). But for me it means Total Waste Of Time (sorry about all the caps…don’t worry, it’s not Part Of A Nigerian Scam LOL). Have a blue day!

  • Ed Buckner

    Somewhere between “in the ballpark” and a guess would be a SWAG. That is a scientific wild-assed guess. It’s uncontrolled, but it is based upon scientific knowledge.

  • Jayati

    Sub : Estimate vs. Guess – DailyWritingTips

    This was a good post, there’s also a new hybrid word that is used now a days in the corporate world, GUESTIMATE – which is midway between the two ( I guess ! )

    Thank you , really enjoy reading these posts everyday !

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