By the numbers: Learn these rules for clearer business writing

Numbers are an integral part of many business communications, but knowing when to spell them out versus when to use figures can be confusing. In general, when writing short items that will probably be read on smartphones or tablets, use numbers because space is at a premium and easy reading is a priority. For longer communications, it’s best to revert to a more formal business style. You can take the guesswork out of writing numbers by following one general guideline and remembering the major exceptions to it. The starting point is to spell out numbers under 10 in text. The company has five offices in Asia. For numbers 10 and above, use figures. The company operates in more than 150 markets. This guideline also applies to ordinal numbers, so spell out first through ninth and use figures starting with 10th. That’s easy enough to remember. Now, here are some exceptions to this rule you will frequently encounter in business.

• Spell out any number that begins a sentence: Eighty-four employees attended the conference. (Remember to use hyphens between words that form one number: twenty-three, forty-one.) If spelling a number would make the sentence awkward, then put a word or phrase in front of the number so it doesn’t start the sentence. For example, to avoid writing 2013 was a banner year for the company, change the sentence: In 2013, the company had a banner year.
• Spell out (and hyphenate) fractions in amounts less than one when they appear in text: Approximately one-third of employees work remotely. Use words or numerals according to an organization’s practice: 3M, Twenty-First Century Foundation. Likewise for official or legal references: 401(k), 10-K.
• Use figures when you write numbers in a series, even if one of the numbers is below 10. The director has 3 assistants, 10 managers and 12 account executives reporting to her.

Also use figures, no matter the denomination, for:

• Money ($2 million, 5 pence, 20 euros)
• Slides, charts, graphs
• Percentages (1%, 99%)
• Figures that include decimals (2.8 million tablets)
• Ages (The new CEO is 57 years old.)
• Measurements (2 tsp.; 5 inches)
• Data-driven references (8 bits)
• Time of day (1 a.m.)
• Days of the month (Jan. 5)
• Degrees of temperature
• Numbered expressions (Page 1, Chapter 4, Version 8, Section 7)
• Points, scores, ratings.

This post is by Helen Cunningham and Brenda Greene, authors of The Business Style Handbook, An A-to-Z Guide for Effective Writing on the Job.