Spell out numbers from one to nine. Use figures for 10 and above. Follow these rules, even when a sentence contains both types. This includes ordinal numbers, unless in an official title.
He is taking two classes.
She has 40 hours of classes a week.
He has four cats and 12 fish.
This is the sixth Global Ivey Day.
This is the 20th edition of the book.
Spell out first, second, third, etc. , until 10, then switch to 10th, 11th, 12th, etc.
The second annual lecture.
The 10th anniversary of the program.
Use figures for school grades.
Example: Students start applying for university in Grade 12.
Use figures in ages standing alone after a name.
Example: He has a son, Tim, 3.
Level designations take Roman numerals.
Example: The student is in Level II of the course.
En dashes, rather than hyphens, should be used to indicate a range of numbers.
Example: 990–94; pages 179–80; $2,400–$2,700
Use hyphens in phone numbers and no brackets around the area code.
Spell out numbers at the beginning of a sentence unless it is a year. If the number is large, reword the sentence so the number doesn’t begin it.
Example: Seventy-five people attended the info session.
Hyphenate when descriptive.
Examples: A $5-million donation; He donated $5 million.
EXCEPTIONS TO THE RULE: dollar figures ($6 million), page numbers (page 56), addresses (6 Western Road), time (5 p.m.), numbers between 1,000 and 10,000 that can be expressed in terms of hundreds (He wrote a paper of sixteen hundred words. She wrote a paper of 1,584 words).