copywriting - Should numbers be written in numerals or words?

When writing numbers, should we use numerals ("5,000") or words ("five thousand")? I'm particularly interested in how easy each is to read and interpret, and whether it's an important consideration for dyslexic users.

Answer

In most cases it's preferable to use numerals. Numerals have a number of advantages that aid readability:

• It's more compact for large numbers (three thousand three hundred and thirty three).


• They stand out among text, which is beneficial because numbers tend to be a key element in a text. I've got ten marbles. I've got 10 marbles. The word ten is as visible as all the other words, but if you go for numerals it's immediately obvious there are 10 of something.


• They can be compared more easily. Three thousand three hundred and thirty three plus one is three thousand three hundred and thirty four. 3333 plus 1 is 3334. This is in line with my first point but also works for small numbers.



• We're so used to numerals, reading and counting with numbers, most people will have to translate the words to numerals in their mind to be able to parse their meaning.


• All this together makes me think numbers should be preferable for dyslexics as well. Having to deal with less text and having a much smaller and simpler string to parse should probably help them deal with numbers*.

*I had a short look for some data on how reading numbers is affected by dyslexia. Obviously there is a big chance you're going to have issues with numbers in terms of sequencing and associating meaning to symbols. See also the International Dyslexia Association on the impact on math. But it doesn't seem to always be the case. In fact, apparently we process text and Arabic numerals using mostly different and separate pathways in our brain (studies from Oxford Journals and Taylor&Francis). This would suggest that if your dyslexia affects the reading of Arabic numerals, having to deal with the simpler shorter strings of the numerals would still be preferable over numbers in words. But there is a chance that some people with dyslexia will be able to deal with Arabic numerals much easier than words.