One, two, skip a few, ninety-nine, 100
Numbers are everywhere. They’re incredibly important for conveying information in a quick and meaningful way, and they’re connected to almost everything we do. We use them to measure weeks, hours, seconds and years; to rank results; and determine how likely something or other is to happen.
Given their ubiquity, it’s unsurprising that there are many ways to deal with numbers in writing. And that these differ depending on subject matter and context.
Know your numbers
The first thing to know when you’re dealing with numbers is how to write them.
If you’re spelling numbers out, remember that compound numbers must be hyphenated. This applies to all numbers from twenty-one to ninety-nine.
When using numerals or digits, there should be a visual separator to demarcate every thousandth integer. In other words, where a number consists of four digits or more, there should be a space or comma every three digits. For example:
1 000
100 000
1 000 000
Where a large number is indefinite (not exact), it is always spelled out. For example:
“There were thousands of wildebeest crossing the river.”
Three, two, one, go!
The most widely applied rule is to write numbers one to nine out and use numerals for 10 and over. In other words:
Single digits must be written out in full, while double digits and higher can be presented in numerals.
Another approach is to write numbers one to ninety-nine in full and use numerals for 100 and above. This application is less common than the first, but is also acceptable.
The bigger the better
For very large numbers (usually over a million), it’s acceptable to use a combination of numerals and text to ensure ease of reading. However, this flips some of the previous rules on their heads. For example:
“Nearly 2 million people around the world marched to show their support for environmental change.”
Getting started
It’s best to avoid starting a sentence with a number. If that’s not possible, write the number out. This rule applies regardless of the size of the number. For example:
“Fifty-five thousand people tuned in to watch Dinner for One on New Year’s Eve.”
Note: Where a number that starts a sentence is followed by a unit of measurement, that unit of measurement must also be written out in full.
From 0 to 100 in 5 seconds
There are often instances where you’ll need to use various numbers in the same sentence or paragraph. What’s important here is to ensure consistency to prevent any confusion. The general rule is that the way numbers are presented should be consistent with the rest of the document. For example:
“The study found that one in 3 500 males is affected by duchenne muscular dystrophy.”
One on top of the other
Sometimes is necessary to have two of the same number appear alongside each another. Naturally, this can cause confusion. In these cases, it’s best to write one number out and use numerals for the second. For example:
“There were twelve 12 square metre stalls available for the tech show.”
“This experiment requires four 4 millilitre pipettes.”
TL;DR
- Numbers one to nine should be written out in full, while 10 and over should be in digits.
- Large numbers use a combination of digits and written numbers.
- Avoid starting a sentence with a number. But if you have to, spell it out.
- Keep your treatment of numbers consistent.
- If two of the same number appear alongside each other, spell one out and present the other in numerals.
