There are many rules regarding the use of written numbers and when to use numerals instead. But before we get into that, let’s discuss the difference between the terms number and numeral. A number is a statement of quantity and can be expressed through the use of both letters and numerals. Numerals, therefore, are the digits, the actual symbols which represent the number.
The Difference Between Numbers & Numerals
Fifty is a number.
50 is a numeral.
Since there are so many rules about when to write numbers, I will stick to the basics and try to keep them simple.
When To Use Numbers & Numerals
The first rule is one that is often debated. Some people say that single-digit numbers should be written and that anything above 10 should appear in numerals. Others say that one-word numbers should be written and that two-word numbers should appear in numerals.
My personal preference is to write out numbers up to and including twenty. Twenty-one is the first two-word number and should appear in digits, as well as anything above that.
You may have noticed that I did not use numerals to express the number 21 in the previous sentence.
Writing Numbers In Practice
Rule number two. Never begin a sentence with numerals. If you have to write a really big number at the beginning of a sentence, you should write it out or re-arrange the sentence so that the number does not begin the sentence.
✘ 10, 000 troops marched into the city that day.
✔ Ten thousand troops marched into the city that day.
✔ That day, 10,000 troops marched into the city.
If you have to include two numbers right next to each other, spell one and digitize the other. For example:
We tested thirty 14-year-olds is easier to read than
We tested 30 14-year-olds.
If you are making comparisons involving two numbers in a sentence, be consistent about writing out or using numerals, no matter the size of the number.
✔ This is 5 inches and that is 23 inches.
✔ This is five inches and that is twenty-three inches.
✘ This is 5 inches and that is twenty-three inches
Decimals, fractions, dates and times should be written as numerals (any instance where a numeral is combined with symbols or letters).
Her temperature is 101.2 degrees, but it’s going down.
The recipe calls for a ½ cup of sugar.
They were married on March 20th, 1985.
I put the roast in the oven at 2:45pm.
Large numbers and numbers used in combination with symbols should be written in numerals.
The car cost $56,452 plus tax.
The interest rate went down to 5%.
Other numbers that appear in your writing should appear as simply as possible. Use your judgment and make sure it is clear, consistent, and easy to read.