When we write an essay or story, we usually assume we’re working only with words. However, numbers have a way of creeping into our writing, much like they do in everyday life. Whether it’s dimensions or dollar signs, writers need to know how to format numbers. When do you use numerals as opposed to words? Unfortunately, this can sometimes be tricky.

There are actually two main rules for numbers; you can choose which one works best for you. According to the Chicago Manuel of Style, you can either spell out all single-digit numbers under 10 or you can spell out all numbers under 100. I usually spell out numbers under 10 because it’s what I’m used to, but either one is correct as long as you remain consistent. You can’t use both rules in one paper.

Although these are good rules of thumb, they only apply to nice, simple numbers. Always put decimals in numerals; for the love of God, always put decimals in numerals. No one wants to read “seven point three hundred forty-two thousandths.” Have pity on your readers and use 7.342.

Another thing to keep in mind is to always spell out “hundred,” “thousand,” “million,” etc. The number in front follows the original rule. For instance, you would write “nine thousand” and “247 million.”

There are three more rules to follow with numbers:

• Always spell out a number if it’s the first word in a sentence.
• Always put years in numerals.
• Always spell out numbers in dialogue.

Simple, right? These are the general guidelines to follow for numbers. However, if you run into a difficult case, the Chicago Manuel of Style will most likely have the answer. If you’re one of those people pursuing a career in science, math, or any other field that spends a lot of time dealing with numbers, you may have to write papers that are almost exclusively figures and equations. In that case, the APA manual might be more helpful. It gives very specific instructions for how to format large amounts of complicated numbers.

In general, these rules are a pretty good starting place for a great paper. Well, not necessarily a great paper but one that uses numbers correctly. The rest of your grade depends on you.