When Should I Spell Out Numbers?

It is generally best to write out numbers from zero to one hundred in nontechnical writing. In scientific and technical writing, the prevailing style is to write out numbers under ten. While there are exceptions to these rules, your predominant concern should be expressing numbers consistently.

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Numbers can disrupt readability in a paragraph, so for most writing purposes, it is best to flex those fingers and type out numbers less than 101 as fully spelled words.

Sophie said there are ninety-nine reasons why she adores Justin Bieber, not nine.

According to census records, there were 53,364 people over the age of one hundred in the US in 2010.

When writing out numbers between forty and forty-nine, be sure to remember that forty has no u in it (this is a common spelling error).

The rules demonstrated in the examples above are simply rules of thumb and there are exceptions to them. For example, round numbers such as hundreds, thousands, or hundred thousands should be written out in full. Numbers that are not conveniently round will read better written as numerals.

It was said that there were five loaves and two fish to feed five thousand men.

This year’s parade brought in 123,675 attendees.

When a number begins a sentence, that number should always be spelled out. That said, writers often choose to restructure their sentences when the numbers become cumbersome for the reader.

5 finalists will qualify for the next round of the competition.

Five finalists will qualify for the next round of the competition.

Seventeen seventy-six was the year America became a nation.

In 1776, America became a nation.

Spelling out numbers in technical, scientific, and complex writing

Scientific and technical journals, and even news reports, often adhere to the rule that only numbers less than ten should be written out in full, except when fractions or decimals are involved. This can be a sensible approach to ensuring the readability of texts that refer to numbers and figures frequently.

The color blue was preferred by five out of eleven experiment participants.

Did you know the average snail moves at 0.029 miles per hour?

Fractional quantities of larger numbers, such as those in the millions and billions, are most easily read when abbreviated as decimals in combination with the word “million” or “billion” where possible. Whole millions and billions (and in American usage, trillions) can be expressed as a whole number plus the word “million,” “billion,” etc.

The Milky Way is approximately 13.6 billion years old.

Canada has a population of nearly 36 million.

When using abbreviations for units of measurement in your writing, always express numbers as numerals. Similarly, when writing about money, use numerals in connection with the dollar sign or other currency symbols. Infrequent references to money read best when written out as spelled-out numbers plus the word for the currency involved.

One inch is equal to 2.54 cm.

The weight of an average hippopotamus is 1,500 kg.

Patients expressed a desire to take the medication occasionally, but were hesitant to pay the fifty-dollar fee.

The actual cost of the medication to patients is $51.75.

Deciding whether to write out numbers in full can be tricky, but the key is to use the correct style for your audience and to use it consistently.