It’s a generally accepted rule that numbers one to ten are spelt out as words whereas numbers over ten can be shown as a figure. That convention aside, however, much simply comes down to your personal preferences.
Round numbers and approximate amounts can be expressed in either words or figures. For instance:
“More than 29 million people have now received at least one dose of a coronavirus vaccine[1].”
But, whichever style you choose, try to be consistent within the sentence. For example:
“During the survey, the traffic team counted around 60 lorries, 300 cars and eleven motorbikes” would be wrong as it mixes letters and numbers. However, “During the survey, the traffic team counted around sixty lorries, three hundred cars and eleven motorbikes” would be correct as it’s consistent.
So far, so simple!
Exceptions
But, as always, there are exceptions to the rule.
One is where two or more numbers are next to each other. This would just look weird. For instance:
“The estate agent was selling 4 2-bedroom apartments for under £200,000 each.”
Instead, it’s clearer to write, “The estate agent was selling 4 two-bedroom flats for under £200,000 each”. Or, even better, avoid figures altogether: “The estate agent was selling four two-bedroom flats for under £200,000 each.”
This is just one of the many writing rules a copywriter is expected to know. So if you’d like professional help with your marketing communications, please get in touch to discuss working together.
[1] https://www.bbc.co.uk/news/health-55274833