Writers often ask themselves when is it appropriate in formal writing to express numbers as figures or digits and when to spell out numbers as words. Namely, when do you write seven and when do you write 7?
Numbers versus Numerals
It is important to understand the difference between a number and a numeral. A number is an abstract notion while a numeral is a specific symbol that is used to express a particular number. “Eight,” “8,” and “VIII” are all symbols that express the same conception of the number.
Spell Out Small Numbers
Smaller numbers, such as whole numbers that are less than ten, should be spelled out. Smaller numbers that are not spelled out are more appropriate for informal writing, such as text messages.
Incorporating Estimates or Rounded Numbers
When including rounded numbers that are over a million, write it as a numeral plus a word. Write “Roughly 8 million people live in New York City,” rather than “Roughly 8,000,000 people live in New York City.”
Numbers with Hyphens
There is no standardized rule in dictating when one-word numbers should be written out. However, most writers adhere to the following rules. One-word numbers such as thirteen or twenty should be written out. While two-word numbers, such as 25 or 32, should be expressed in figures.
An ordinal number is a number that defines an object’s position in a series. For example, “first,” “second,” or “third” are ordinal numbers. Ordinal numbers or generally used as nouns, pronouns, and adjectives in writing. When using ordinal numbers in formal writing, spell out the number. For example, write, “She earned second place in the tournament,” rather than “She earned 2nd place in the tournament.”
Spell Out Decades and Centuries
Decades and centuries should be spelled out. Write the Nineties or eighteenth century rather than the 90s or 18th century.
Recipes and Everyday Writing
In everyday or informal writing, such as writing recipes, use digits: “Add 4 cups of chopped apples” or “10% of schools.” In formal writing, however, spell out the percentage, such as “ten percent of students.”