Numbers in written work – what are the rules?

Even the most non-scientific academic writing will contain numbers, and there are a series of rules and conventions about how they should be presented. Knowing the rules and applying them consistently will help to make your work look mature and academic – and will save you some head-scratching!

Have a look at these sentences:

1. 59% of respondents surveyed felt that exams had become easier over time.
2. 1967 was the height of the hippy era.
3. It is reported that 1000s of people fled from the war-torn zone.
4. I usually check that my door is locked at least 3 times.
5. ½ of students miss early lectures because they can’t get up on time.
6. I teach a class of 12 year old students.
7. The thief stole 20 15 kilogram bags of compost.

How do you think they look? Are they a bit ‘untidy’? Which do you think are right and which wrong?

Well, according to most academic style guides, they are all wrong! Although there are some variations between institutions, publishers and editors, the correct formats would probably be as follows:

1. Fifty nine per cent of respondents surveyed felt that exams had become easier over time.

Although it is most usual to present numbers higher than nine in figures, if the numbers come at the beginning of a sentence they should be written in words. Alternatively you could change the way the sentence is written – in this case you could write: Of the respondents surveyed, 59 per cent felt that exams had become easier over time. Note that in non-technical subjects it is usual to write ‘per cent’ (or ‘percent’ in US English) rather than using the % sign.

Here are the correct formats for the other sentences:

1. The year 1967 was the height of the hippy era. (In informal writing it would be fine to start this sentence with ‘1967’, but in academic or other more formal writing it is better to change the sentence construction.)
2. It is reported that thousands of people fled from the war-torn zone.
3. I usually check that my door is locked at least three times.
4. Half of students miss early lectures because they can’t get up on time.
5. I teach a class of 12-year-old students.
6. The thief stole twenty 15 kilogram bags of compost.

The University of Bristol has a really comprehensive resource which explains these examples, and more. Have a go at the practice exercise at the end of the resource page to check your understanding.