“There are three rules for writing a novel,” W. Somerset Maugham once wrote. “Unfortunately, nobody knows what they are.”
If I had to adapt Maugham’s quip to business, scientific and technical writing, I would say, “There is one rule for writing numbers. Fortunately, everyone knows what it is.”
It’s simple: Be consistent.
Here are eight guidelines to help you follow that one simple rule:
1. Spell out numbers less than 10; use figures for numbers 10 and higher (except in scientific and technical writing, where all numbers may be written as figures).
One potato, two potatoes, three potatoes, four — makes 10 potatoes.
2. Spell out numbers that appear as the first word in a sentence (or restructure the sentence to avoid beginning with a number).
Sixty-four bottles of beer were on the wall, 64 bottles of beer.
3. Use figures for percentages (even for percentages less than 10).
We spent 8% of our day putting those bottles on the wall.
Note: Scientific and technical writers prefer the percent symbol, whereas business writers have traditionally preferred the word percent, but increasingly business writers are using the symbol.
4. Use figures for monetary amounts (even for amounts less than 10).
If one of those bottles happens to fall, it will cost you $8.57.
5. Omit the decimals or zeros in even dollar amounts (except for consistency in a table or series).
We’ll round that figure up to an even $9 ($6.57 for the beer, $2.00 for the bottle and $.43 for our boat payment).
6. Write dates as cardinals (even though you pronounce them as ordinals).
The breakage occurred on the evening of December 1, not December 1st.