How to write numbers
While areas such as mathematics, science or economics require you to write numbers in their numerical digits, it is more acceptable in prose to write them in full.
DISCLAIMER: You are, of course, entitled to your own stylistic choice. The examples below provide a guide and demonstrate how I, myself, write out my numbers in narrative prose and my articles.
Whole numbers
In my last full-time job, their in-house style guide commanded us to write out in full all numbers up to ten. Anything from eleven upwards had to be in digits. So any work I produced would look something like this:
She went to the shops seven times that week.
There has never been found a centipede with 100 legs.
However, other institutions or workplaces ask that anything from ten upwards should be in digits. It’s a personal style, but whichever way you choose to work, make sure you’re consistent. It is also worthy to note that, in creative prose, many writers prefer to write out all numbers in full, within reason. For example:
The army was fifty thousand strong.
The torrential rain did not relent for thirteen long and solemn days.
Note that all numbers from twenty-one upwards should be written in compound form, using hyphens.
‘Ninety-nine bottles of beer on the wall, ninety-nine bottles of beer…’
The old man had said he was seventy-five but he moved like he was thirty.
Mixed whole numbers
When writing a sentence which encompasses both single-digit and multiple-digit whole numbers, it always looks neater when you are consistent and spell them both out the same way. So if your personal preference is to write out numbers from ten or eleven upwards in their numeric forms, I would recommend you bend the rules on occasions such as these:
Despite the fact that four of the men were innocent, the court convicted all twelve.
There were only nine girls in the class but fifteen boys.
Fractions
But what about non-whole numbers like fractions and decimals? Outside of maths, science, design, computing and anywhere else where digits are required, simple fractions should be expressed in formal prose like so:
Precisely one-third of all life was wiped out when the aliens first attacked Earth in 2071.
The farmer managed to sell five-and-a-half sacks of potatoes.
Decimals, however, should always be written out in numerical digits for the sake of clarity.
On Tuesday, we released the 1.1 version of our weather app.
The votes were counted and the motion was passed with a whopping 79.4% majority.
Dates
Of course, writing dates is another matter. No writer would express 1965 ‘nineteen sixty-five’, unless in very rare circumstances, such as:
‘How do you say that, Paul? Is it one, nine, six, five or one thousand, nine hundred and sixty-five?’
‘You idiot. It’s nineteen sixty-five!’
When referring to decades, it is best to write them out like this:
The ‘60s were wild.
The sixties were wild.
The 1960s were wild.
Note the lack of apostrophes placed before the ‘s’? If you’re a little confused about this fact, check out my article on making possessives.
Time
When expressing a specific time in prose, how it is best written depends on how exact the time actually is and also the context.
It was half one by the time they were ready to leave.
‘I always leave the house at a quarter to seven in the morning.’
‘I can’t talk for long. My train is due at 8:32.’