Objectives

• Recognize general rules for writing cardinal (counting) numbers in English
• Write numbers in digits and words based on English writing rules for cardinal numbers

In the spelling chapter for counting numbers, we learned the words for cardinal numbers.  When do we write the digits or the words for cardinal numbers? Here are some basic rules.

General Rule 1

When numbers in writing are about

• Dimensions or measurements
• Time–hours, minutes, seconds
• Age
• Percent ( % )

They are usually written as numbers not words. For example,

• A common rug size is 5 feet by 7 feet.
• The appointment is at 8:30 a.m.
• My son was 2 months old when he got his first tooth.
• She passed the class with 88% on her final exam.

Piggy Bank:
a traditional place to save coins.
It is in the shape of a pig.

General Rule 2

Numbers under 10 should be written in words. Use the digits for any numbers 10 and higher. For example,

• The box had nine pieces of chocolate in it.
• The cookie box has 36 cookies in it.
• There were 343 pennies in the piggy bank.

General Rule 3

When a number begins a sentence, it should be written in words. For example,

• There are 19 students in my class.
• Nineteen students are in the class.
• Twenty twenty was the first year of the pandemic.
• COVID caused global lockdowns in 2020.

General Rule 4

A compound number is a number that uses two words for to say the number. Compound numbers should be hyphenated. They require dashes in between the words of the number. For example,

• Twenty-three customers walked in after 8:00 p.m.
• “Forty-two is the meaning of life” is a quote from a funny movie called “The Hitchhikers Guide to the Galaxy”.
• One hundred sixty-three people gave the restaurant a 5-star rating.

General Rule 5

Numbers over 100 do not contain the word and. For example,

• One hundred ten people bought tickets for the show.
• Three hundred forty-three passengers are on the plane.

General Rule 6

When two numbers are next to each other in a sentence, write one in words and use digits for the other number. For example,

• The childcare class had twelve 5-year-olds with two teachers.
• She walked three 1-mile hikes on Tuesdays, Thursdays, and Saturdays.
• The construction project needed seventeen 2-by-4 pieces of wood.

General Rule 7

Numbers in the millions or billions are written with a number and the word. For example,

• The population of earth is approximately 8.2 billion.
• The population of the United States is over 333 million.
• The population of Oregon is about 4.3 million.

If an exact number needs to be written, then numbers without words are necessary. For example,

• Last year, 3,667,758 babies were born in the United States.

General Rule 8

Fractions under one use words and are hyphenated. For example,

• Three-quarters of the bottle is full.
• I need one-half of the potatoes for dinner.

Mixed numbers are written in digits. For example,

• The boss told me to move the 2 ¹/₂ cases to the front of the store.
• I need a piece of wood 3 ³/₄ feet long.