1. Grammar Rules for Writing Numbers
Jenkins English

2. Numbers That Are Spelled Out
Please note that there are some exceptions to the rules outlined below. As with other grammar rules, rules for writing numbers change according to certain style guides (i.e. Chicago Manual of Style, AP, MLA, etc.). However, here are some general rules for spelling out numbers.

3. Numbers under 10:
Martin has two younger sisters and five older brothers. Note: Some style guides recommend spelling out the numbers one to one hundred.

4. Numbers at the beginning of a sentence:
Sixty children came to the class trip last year, but this year there were 80.

5. Fractions (usually hyphenated):
About one-third of the class comes from China. Note: However, the exception to this rule is when it is a mixed fraction. We then use numerals (unless it comes at the beginning of a sentence). Example: The recipe calls for 1 ½ cup of nuts.

6. Numbers 10 and above:
She has bought about 12 pairs of shoes and 15 dresses in the last three months. Note: However, when numbers are in a list it is best to keep all the numbers in the list consistent, even if numbers are under 10.
Correct: She has four brothers aged 5, 7 12, and 15.
Incorrect: She has four brothers aged seven, nine, 12, and 15.

7.  Dates and Years:
School begins on August 27, Note: We do not use ordinal numbers (i.e. 1st, 2nd, 3rd with full dates).
Correct: The play is on March 23, 2010.
Incorrect: April 1st, 2001.

8. Sequence
Make a habit of never using 1st, 2nd, etc. as first, second, third are generally going to fit most style guides and also look much better on the page.
Correct: He tried at first to hit a ground single, if only to make it past first and second base.
Incorrect: 1st, we left for the market. 2nd, we went to the mall

9. Percentages:
According to the latest survey there are 52% of teachers who live in the city.
Note: However, if a percentage begins a sentence, it should be spelled out. Example: Fifty-two percent of students walk to school.

10. Decimals:
There was 0.73 inches of rain last month.

11. More Than One Rule
The following are special cases and are often written in multiple ways.

12. 2010s Decades: She lived in San Francisco in the eighties.
During the 1980s she lived in San Francisco.
She lived in San Francisco in the ‘80s.

13. 8:15 A.M.
Time:
We usually spell out the time when it is followed by o'clock or when a.m. or p.m. is not mentioned.
He arrived around five o’clock
However, we use numerals when we need to emphasize the exact time and when using A.M. and P.M.
He arrived promptly at 8:15 A.M.

14. Examples: o'clock
Correct: We have to get up at six o'clock to be on time for school.
Correct: She gets home around eight in the evening.
Incorrect: We have to get up at 6 o'clock to be on time for school.

15. Examples: a.m., p.m.
Correct: The accident happened at 8:22 P.M. last night.
Correct: They did not leave the party until 2 A.M.
Incorrect: He didn’t get there until nine-seventeen A.M. that morning.

16. Noon and Midnight
 We usually spell out noon and midnight instead of writing 12:00 p.m. and 12:00 a.m.
Correct: We came home around midnight and slept until noon the next day.
Incorrect: I can’t stay out past 12:00 AM because I will get in trouble.

17. Large Whole/Round Numbers:
If there are only a few words, we often spell out.
 Examples:
He earned two million dollars last year. or He earned $2 million dollars last year.
Can you loan me twenty dollars?
 For larger numbers we write in numeral form ($5, 385, 673)

18. Final Note
When in doubt about whether to spell out or write numbers, it is best to consult a style guide. Also, you usually can rely on spelling out no matter what your question.

19. Citations
MLA
OWL at Purdue
Grammar Girl

20. Directions:
On your handout, come up with one Multiple choice questions that would test someone’s knowledge of using grammar rules to write numbers.
Pose the question to your neighbor.
Read your neighbor’s question and see if you are correct.