How to write numbers in non-fiction and memoir

Have you ever wondered when you’re supposed to use digits and when to write out numbers in non-fiction? Perhaps this isn’t something you’ve considered before, but now you’re wondering whether your manuscript contains an unintentional mixture of the two and you have no idea how to put it right.

I can help with that!

I’ll guide you through the standard principles for how to write numbers in non-fiction − with a special section dedicated to memoir.

Why am I treating memoir separately to standard non-fiction?

When I first started copyediting memoir, I found myself getting in a bit of a muddle over which rules to follow, because although memoir is non-fiction, it uses elements of fiction like dialogue. I’ve used what I’ve learnt to come up with my own style sheet for numbers in memoir for you to take away and use.

General principles for numbers in non-fiction

While there’s a healthy dollop of ‘it depends’ (an editor’s favourite phrase) when it comes to style, there are also some general principles you can follow for whether you should use words or digits when writing numbers in non-fiction.

And what’s the number 1 rule when it comes to editing and proofreading? Consistency! So if you don’t agree with my guidelines (it’s totally cool, whatever), just please promise me you’ll use the same approach throughout your book or content.

Let’s start with the easiest rule first: if you’re writing web copy (like a blog post or webpage on your website) you can get away with just using digits. Easy-peasy!

Now let’s take a look at printed works.

In general non-fiction, it’s fairly standard to use words up to either ten or one hundred, and digits thereafter (your choice which one you go for). If your sentence has a combination of the digits vs word rule, go for the range that uses digits, i.e. ‘There were between 8 and 15 cats in the house’ NOT ‘There were between eight and 15 cats in the house.’

For data and specific numbers, however, always use digits, no matter what the number: ‘My glucose level was 4.3 when I woke up.’

If you’re self-publishing your non-fiction book, there’s nothing stopping you using digits throughout, if you just don’t like the combination of digits and words.

A proofreading rule across any type of written content is that you should NEVER start a sentence with a digit – so instead of ‘1986 was the best year to be born’ it should be ‘The best year to be born was 1986’. But I think the preference for digits in web copy is making this rule harder to follow in print.

Photo caption: Siân Smith

More examples of writing numbers in general non-fiction

A lot of these more specific rules will depend on your style guide. I mainly work with Oxford style (New Hart’s Rules) and Chicago style (Chicago Manual of Style, often abbreviated to CMOS); I summarize each of these styles here for you.

Do not let this overwhelm you.

Editors like myself honestly thrive on this sort of stuff! If you’re the kind of person who likes to spot and follow a rule, by all means choose your style and follow it. Otherwise, let your copyeditor sort this for you 😉 

Oxford style for numbers in non-fiction

(New Hart’s Rules 11.1.2)

• Non-technical texts: words below one hundred, digits thereafter.

• Technical texts: words up to ten, digits thereafter (but exceptions apply, depending on the subject matter).

• Large round numbers expressed either as a combination of numbers and words (6 million, 1.5 billion) or entirely as words (six million, one and a half billion).

• For approximations, it’s best to use words (‘about a thousand’, rather than ‘about 1,000’).

• Words for informal phrases or idioms (‘six of one, half a dozen of the other’).

• A combination of words and digits can be necessary for clarity, i.e. when two different categories are referred to (‘I ordered thirty 20-page brochures’).

• Use words for ordinal numbers (first, second, third, etc.).

• Use digits for ages expressed as cardinal numbers (‘a 33-year-old’, ‘the girl is 15’) but words for ordinal expressions (‘in my twenties’, ‘twenty-first century’).

• Less formal or more discursive texts usually prefer words for anything to do with age (like memoir!).

Use digits for:

• Parts of books (chapters, pages, plates: chapter 7, p. 10).

• Numbers of periodicals or journals (New Scientist 67).

• Scores of games (‘we won 3–0’).

• Distances of races (the 100-metre sprint, 10k).

• Houses and building numbers (52 Smithson Street).

• Road and highway numbers (the A435, the M42).

How to punctuate numbers:

• Hyphenate compound numbers (seventy-seven, one hundred and thirty-nine).

• In non-technical texts, use a comma in numbers of four figures or more (1,200; 62,786; 121,000).

• No commas in years until you reach the ten thousands (2025, but 10,000 BCE).

• No apostrophe needed to pluralize numbers (‘the 1980s’, ‘count in threes’, ‘she lived to be in her nineties’).

Photo credit: Siân Smith

Chicago style for numbers in non-fiction

(CMOS 9)

Chicago style refers to a general rule and an alternative rule

General rule: non-technical texts, use words up to one hundred.

Alternative rule: more technical texts can spell out single-digit numbers (zero to nine) and digits thereafter.

• Round multiples of hundreds, thousands, and hundred thousand are typically expressed as digits with this zero to nine rule.

• Use words for hundred, thousand, hundred thousand and approximations (‘for the past two thousand years’; ‘around forty thousand people packed into the arena’ vs ‘there were 47,811 ticket holders’).

• Large round numbers will depend on whether using the general or alternative rule.

• General rule: fourteen million.

• Alternative rule: 14 million.

• If a sentence uses a fractional quantity with a round quantity in the millions or billions, use digits for consistency: ‘between 2 million and 2.2 million’.

• If the text has multiple references to large numbers, digits may be preferable.

• CMOS is more forgiving with starting a sentence with a year (‘1986 was the best year’), but it’s preferable to reword (‘The best year was 1986’).

• Sentences can start with a term that combines letters and digits (‘5G signal is the best!’).

• Cardinal numbers follow the general or alternative rule for numbering.

• General rule: ‘The office was on the fifteenth floor’; ‘the 105th day on the road was hard’; ‘I won a prize for being the supermarket’s ten thousandth customer’!

• Alternative rule: ‘The office was on the 15th floor’; ‘the 105th day on the road was hard’; ‘I won a prize for being the supermarket’s ten thousandth customer’ (words for round multiples of hundred, thousand, etc.).

• A combination of words and digits can be necessary for clarity, i.e. when two different categories are referred to (‘I ordered thirty 20-page brochures’).

• Where a sentence or paragraph uses many numbers, use consistency in favour of digits (i.e. if just one number uses digits according to style, then all numbers should be digits).

• If there is a cluster of numbers, preference for digits is advised. This avoids a clunky sentence.

Use digits for:

• Abbreviated units of measure (3 kg).

• Before the word ‘percent’ (‘per cent’ in British English) (5 percent).

• Parts of books (chapters, pages, plates; chapter 7, p. 10).

• With symbols (£5, 8%).

• Streets, rooms (room 16).

• Dates (5 May, 5th of May).

• Clothing sizes (size 14).

• Scores and vote tallies (‘we won 3–0’, ‘the vote was 18 to 9’).

Physical quantities in non-fiction for general readership (non-technical):

• Follow the general rule for measurements such as distances, lengths, etc.

  • It took less than twenty minutes for the temperature to drop by twelve degrees.

  • The car hurled around the corner at fifty-seven miles an hour.

  • At five feet four, I’m the shortest in my family (five foot four also acceptable for more colloquial texts).

• Follow the ‘commonly expressed’ rule for other measurements where digits are usually used:

  • My husband has a 36-inch inside leg.

  • A right angle is defined as an angle of 90 degrees.

  • This car guzzles fuel at 35 miles to the gallon.

Before I guide you through the somewhat hybrid form of memoir, you need to understand the general rules for numbers in fiction, because memoir blends the numbering rules for non-fiction and fiction.

General principles for numbers in fiction

In fiction, numbers are usually spelled out, especially in dialogue. The general exception here is the same as with non-fiction, i.e. if the number is specific, such as telling time on a digital clock or precise money amounts (£2.57). More details on these exceptions in the next section.

The same rule of avoiding a sentence starting with a numeric number applies.

Photo credit: Siân Smith

How to write numbers in memoir

Here we go then, my guide to writing numbers in memoir. Rather than giving you lots of choices, I’m just going to share my personal style sheet for how to write numbers in memoir. Please do use this style sheet for your own memoir or editorial business, or adapt and change as you think feels right.

Memoir comes under the non-fiction arm of life writing, which also includes biography and autobiography, so you could also use this style sheet for those genres.

If you want to come up with your own style sheet for life writing, I highly recommend starting with Amy Schneider’s book The Chicago Guide to Copyediting Fiction, it is soooo helpful for that grey area of dialogue and numbers in memoir. I’ve based many of my decisions on her detailed book, but have also deviated in a few places.

Style sheet for numbers in memoir

Use WORDS for:

• Ages (‘in my forties’, ‘on my thirty-eighth birthday’).

• Dialogue (with a few exceptions, see below) – consider how the speaker would say it, e.g. ‘Fifteen hundred’ or ‘one thousand five hundred’; ‘a hundred’ or ‘one hundred’?

• Height (consider if you want to use the more technical ‘five feet four’ vs the colloquial ‘five foot four’).

  
  

Use DIGITS for:

• Years.

• Numbers in messages, notes, screens, on a sign (e.g. text messages, a hand-written note, a diary entry, a sign saying ‘Back in 5’).

• Clothing and shoe sizes.

EXCEPTIONS

• Decades – this depends on whether you are saying ‘the nineties’ (words) or ‘the 1990s’. If you are only referring to decades from the twentieth century, choose either and then stick to one. If you refer to decades from multiple centuries, use numbers.

• Time

  • Predominantly use words, unless for precise times or digital clocks – compare ‘I woke up around five a.m.’ versus ‘My alarm was set for 05.00 a.m.’.

  • Words for times on the hour and quarter hours: ‘one o’clock’, ‘quarter past two’. Format times as a.m./p.m.

• Dates

  • Use digits in general narrative, ‘17 June 1986’ and follow the same rule as for numbers in messages, notes, etc.

  • Use words in dialogue, ‘seventeenth of June 1986’

Speaking in numbers – the exceptions of writing numbers as words in dialogue

Use digits in dialogue for the following:

• Years: ‘Stop saying 1986 was the best year ever!’

• Numbers with decimals: ‘You knocked off 2.3 seconds from your personal best!’

• Brand names: ‘Better get some WD40 on that squeaky door.’

• Numbers on display: ‘I could see the speedometer creeping up to 50 mph.’

• Specific times: ‘My phone said it was 05:06.’

• Course numbers: ‘Are you also taking English 201?’

• Phone numbers.

• Road numbers: ‘We hurtled down the M42.’

Numbers in personal development and memoir hybrid

If you’re writing a hybrid of personal development and memoir, you may have pages with exercises you want your reader to do (like a breathing exercise). For instructions like this, I prefer using digits:

-          Count in for 4.

-          3 ways to reduce your stress (yes, we’re ignoring the rule about not starting a sentence with a digit).

-          Day 1, Day 2, etc.

If this was in more general text, I stick to words:

-          General copy: ‘Many of us struggle to come up with just three things we like about ourselves’.

-          Instruction: ‘Write down 3 things you like about yourself’ [followed by space on the page with 3 lines].

EXCEPTION: The combination rule may be needed here, however: ‘Repeat step 1 three times’

You may certainly need to breathe in for a count of three (or four) after making it through all of that! Hopefully that’s offered a bit of clarity on how to write numbers in your non-fiction book or memoir, or at least inspired you to think about your preferences when it comes to self-editing or working with an editor.

Do let me know in the comments or send me an email if there are any other specific examples or rules you’d like me to add. I’d also love to know your personal preference when it comes to writing numbers in non-fiction and memoir!