style guide: writing numbers

When writing numbers you want to strike a balance between making it something that sounds natural in English and yet is easy to read.

Avoid using numbers when you can. Most people cannot picture or care much about numbers over 12.

But when you must use numbers here are some guidelines:

For the numbers ten and under, write them out in English:

My father is three-eighths Cherokee. He has two brothers.

Exceptions:

• page numbers (page 5)
• percentages (5%)
• decimal numbers (5.02).

For numbers over ten, use figures:

My mother is 71 years old.

That “71” is much easier to read than “seventy-one”.

If some numbers are under ten and some over, then write them all as figures:

I have 16 dogs, he has 2.

Always write out numbers that begin a sentence:

Four score and seven years ago.

Unless your subject demands it, keep your numbers rough. It is better to say, “There were about 200 people in the room” than “There were 203”.

You can write “m” as short for million:

America now has 300m people.

But always write out billion:

The Iraq war will cost more than $80 billion.

Use billion to mean a thousand million and trillion to mean a thousand billion:

• hundred 100
• thousand 1,000
• million 1,000,000
• billion 1,000,000,000
• trillion 1,000,000,000,000

In India, a crore is 10 million, a lakh is 100,000.

Write centuries as figures:

The Arab empire rose to power in the 600s.

Toynbee would say “in the seventh century after Christ,” but “600s” is shorter and easier to understand. And no one has to remember that the seventh century are those years that begin with six.

Write decades this way:

My mother was a flower child in the 1960s.

That rather than ’60s or Sixties or whatever.

In general, if something happened in the last ten years, give the year, if in the last century, the decade and before that, just the century:

• I read “War and Peace” in 1998.
• I read “War and Peace” in the 1980s.” (it was in 1987, but who cares?)
• Tolstoy wrote “War and Peace” back in the 1800s.

But the level of detail you are writing at matters. If you are telling Tolstoy’s life story, then give the year. But remember that most people do not care about years from before their birth. The year 1852 is as meaningless as 1853.

If you give the day, write it this way:

Friday April 13th 2007

No commas required.

Write exact times this way:

11.35pm

Ranges: Write ranges of numbers the way you would say them when speaking:

I lived in New York from 1981 to 1997.

Do not write something like this:

I lived in New York 1981-97.

That is not even English: no one talks like that.

Of course in real life you would say this:

I lived in New York from ’81 to ’97.

But it makes it easier for your readers if you write out the year in full. It requires less thinking on their part.

See also:

• style guide
• number and measure