I used to love doing fractions in math, geek that I am. Some people just don’t comprehend them. Some people don’t even know how to write fractions, either in words or in numbers.
When expressing fractions in words, hyphenate.
Examples: one-half, two-thirds, three-quarters
If combined with a whole number or units of measure, use numbers.
Examples: 2½ times as large, ¼-in. hole
Sometimes Word will automatically convert 3/4 to ¾, and if it doesn’t you can usually insert a symbol to “fractionalize” a common fraction. Others, such as 11/16, don’t do it automatically. It’s generally best to leave them “unfractionalized,” putting a space between the whole number and the fraction, to avoid erroneous symbol translations when used in electronic form.
Note: hyphens do not belong between the whole number and the fraction.
Bad Example: 13-3/8 in.
The correct form is 13 3/8 in. or 13 3/8-in., depending on whether it is used as an adjective or not.
Used as adjective: The 13 3/8-in. tubing was run into the hole.
Not used as adjective: The diameter of the tubing was 13 3/8 in.
Fractions are not used with metric system units. Rather, decimal notation is used.
Note: Always use a zero preceding the decimal point for numbers smaller than 1.0.