Guestimate, Guesstimate

Which Is Best? To Guess, to Estimate, or to Guesstimate?

by Owen Fourie

A student stared at her graded economics research paper. What she had thought was the perfect essay turned out to be a fiasco.

One thing she saw immediately was that wherever she had used the word guesstimate, it had been deleted. “Use guess or estimate,” said her professor’s terse note.

New words

The English language isn’t set in concrete. It is a vibrant language that coins new words to keep up with the pace of change.

Dictionary editors read many publications, daily, searching for new words and new usages of old words. They record these and track their occurrence in various areas of life.

After many years have passed, some of these new words and new usages of old words will make their way into the dictionaries. Sometimes, a few will be included in a relatively short time—think of google.

Even then, the new word might be recorded as “informal,” meaning that although it has gained recognition in a dictionary, it is still not acceptable in formal speech and writing. That takes much longer.


This is certainly so in the case of guesstimate.

It was coined in the 1930s. Although it appears in dictionaries, it is still indicated for informal usage.

Guesstimate or guestimate is the obvious combination of the two words guess and estimate.

It follows the different pronunciations of estimate as a noun and as a verb:

  • As a noun, it is GUESS-ti-mit;
  • As a verb, it is GUESS-ti-mate.

When you use this word (only in informal contexts), what you are saying is

  • you do not yet have all the facts and figures in a given situation, or
  • you have only incomplete information with no likelihood of receiving better data;
  • you are, while basing your estimation on incomplete information, bringing some guesswork into the matter to present as complete a picture as possible.

Dictionaries and formal writing

It is necessary to consult a dictionary when you write a formal paper to be sure that you are not using informal, colloquial, or slang expressions.

Simply because you hear such words used does not mean that they can be used in your essays.

Even if a word appears in a dictionary, it does not mean that it belongs in your essay. You have to take note of what the dictionary indicates about a word. If it shows that it is informal or colloquial or slang, don’t use it.

While guesstimate remains informal, use guess or estimate with a qualification explaining the lack of any information.


What experiences have you had of using informal words in your formal papers? Your comments, observations, and questions are welcome.

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