When writing a research paper, there are a number of style and formatting guidelines that authors must follow regarding the presentation of numbers. One such guideline relates to whether numbers should be written out or expressed using digits. There is no universally agreed upon rule, as different style guides offer different recommendations. Most provide general guidelines on when it is preferable to write out numbers versus using figures.
The question of writing out numbers versus using digits can seem trivial on the surface, but it does impact readability and consistency within academic writing. Getting it right ensures the reader can easily understand numbers in context without confusion. It also shows the author understands and is following the publishing standards and formatting conventions of their specific field or discipline. With so many considerations involved, determining the best practice can take some research and judgment calls on a case-by-case basis.
General Guidelines from Major Style Guides
Let’s first examine the general guidelines presented by some of the most widely used and authoritative style guides for academic writing:
The Modern Language Association (MLA) recommends writing out whole numbers from zero through one hundred and certain even hundreds, thousands, and larger multiples of them. For any other number, use figures.
The American Psychological Association (APA) has very similar guidelines, but also states numbers that begin a sentence should be written out.
The Chicago Manual of Style recommends writing out whole numbers from zero through one hundred, and any number occurring within a sentence that can be written as one or two words. Use figures for all other cases.
The Associated Press (AP) Stylebook advises writing out numbers one through nine, and using figures for 10 and above, with a few limited exceptions such as in dates, addresses, and page numbers which should always be in figures.
The most common rule of thumb across styles is to write out whole numbers that are easily expressed in one or two words, and use figures for everything else, considering other factors like whether the number begins a sentence. Keeping to these general recommendations will serve writers well in most cases.
Subject-Specific Considerations
There may be exceptions or variations depending on the specific field, subject matter, or intended publication format of the research paper. For example:
In scientific papers, numbers are almost always in figures to avoid ambiguity regarding units of measurement.
History papers may write out larger numbers to help transport the reader to the time period being discussed.
Numbers used for statistical analysis, charts, tables or mathematical expressions should always be in standardized digit form for clarity and consistency.
Professional publication stylesheets may override general rules, so it’s wise to confirm their specific guidance for numbers.
Screen readers have an easier time with figures, so accessibility is improved if numbers in web content err on the side of figures over spelling out.
Considering readability is also important. Very large numbers written out, like eleven million three hundred forty-two thousand six hundred eighty-nine, can become unwieldy and difficult to parse quickly on sight. Figures may be preferable in such cases even if general rules advise spelling out.
Writers should carefully consider any subject-specific recommendations, intended publication format, and readability factors rather than rigidly adhering to general style guides alone when deciding between figures and spelling out numbers in a research paper. Consistency is also vital regardless of approach.
Mechanics of Writing Out Numbers
If opting to write out a number, the following mechanics apply:
Write out ordinals (1st, 2nd, 3rd) rather than superscript (1st) unless part of a date or other standardized context requiring figures.
For decades, century names are preferred over numerals (twentieth century vs. 1900s).
Spelled-out numbers from zero to ninety-nine are one word, while those one hundred and above are two words (ninety-nine vs. one hundred).
In titles, chapter headings and text, initial letters of number words are capitalized (Fifteen Ways vs. fifteen ways).
For compound modifiers, hyphenate number words (twenty-one-year study).
Numbers should not be abbreviated in text unless part of a standardized format like equations.
Commas are used in numbers of 1,000 or more, following standard rules (one thousand, two hundred thirty-four).
Care should be taken joining number words with other words to avoid awkward constructions.
Consistency is also critical, both within a single paper and across related papers in a larger work. The mechanics of writing out numbers smoothly takes practice, so writers may want to run spell check and proofread carefully when first adopting this method.
Maintaining Readability
The goal of any formatting choice should be maximum readability and comprehension, avoiding unnecessary challenges or distractions for the reader. Consider experimenting with both approaches—spelling out and using figures—for different numbers in a draft before deciding the optimal strategy. Similarly, get feedback from others to gauge which approach feels most natural and readable based on factors like:
The intended audience’s familiarity with subject matter concepts
How numbers are distributed and emphasized within text vs. displays like charts
Whether certain numbers require disambiguation or precision in meaning
Natural sentence flow versus numbers disrupting readability
Consistency in approach throughout and across related works
Proper number styling takes the reader’s experience into primary consideration. With practice and by weighing options critically on a case-by-case basis, writers can determine the most readable presentation of numbers for their specific research paper context and intended readers. Ultimately, the goal should be communicating numerical concepts clearly without distraction—a balanced approach is usually best.
Andrew Stroud