Writing Numbers: Whether to enter numerals or words for a number is often confusing. In different situations, this will vary, but probably a fair generality is that a numeral is shorter than a word, so use a numeral, with the following exceptions:
- You cannot begin a sentence with a numeral. The number “1,256,781” must be entered at the beginning of a sentence as “One million, two hundred fifty-six thousand, seven hundred and eighty-one,” as ridiculous as it seems. If the number involves a unit of measure, the unit must be likewise spelled out as a word in most cases (pH would be one exception). Work the sentence so you don’t have to begin it with the number!
- When not speaking of data or experimental groupings, use words instead of numerals for small numbers: “two centuries ago,” “For well over fifty years..”, “Of the many millions of fish released…”
- Numbers are generally written as numerals when a specific value is named, and always when associated with a unit of measure: “270 centuries ago,” “59 people…”, “…47.8 g dry weight…”.