A simple rule for using numbers in writing is that small numbers ranging from one to ten (or one to nine, depending on the style guide) should generally be spelled out.
Larger numbers (i.e., above ten) are written as numerals.
Should you write them out in words or leave them as numerals?
To write numbers properly, you will have to identify potential differences between major style guides (such as MLA, APA, and Chicago, to name a few) because these guides often outline different rules for using numbers in writing. Say you're working on a paper evaluating the importance of the local public library in your community.
Spell out numbers lower than 100 in nonscientific text.
If a number higher than 100 is rounded off or approximated, spell it out in nonscientific copy. An exception to this is online text, where in a way all bets are off.Correct: There were twelve 4-year-old children waiting for the librarian to begin story time.Correct: There were 12 four-year-old children waiting for the librarian to begin story time. If you are referring to a specific year (e.g., 1955), use the numeral.The document will make use of small numbers, large numbers, decades, and statistics.Thankfully, when using numbers in writing, you can count on a few conventions that apply to most situations; just be sure to consult your specific style guide if one has been assigned.Similarly, if a single sentence combines small and large numbers, make sure that all the numbers are either spelled out or written as numerals.Incorrect: The library acquired five new mystery novels, 12 new desktop computers, and 17 new periodicals.The idea of online text is to keep it short, with consideration to search engine optimization and other factors that are beyond the scope of print publications.For online writing, numerals frequently are used in all instances.For example, instead of writing, "It cost ten-thousand four-hundred and sixteen dollars to renovate the local library," you would write, "It cost ,416 to renovate the local library." The reason for this is relatively intuitive.Writing out large numbers would not only waste space but could also be a major distraction to your readers.