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Using Numbers in Scientific Manuscripts

When should you spell out a number in a scientific paper, and when do you use a numeral? Here’s how to follow conventions and be consistent.

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Writing a scholarly manuscript often requires the use of numbers to express important information, particularly in the sciences. Although the use of numbers is largely straightforward, there are a few things to keep in mind. In this article, numeral refers specifically to a number as it is written in mathematics (e.g., 4).

Do not start a sentence with a numeral

When writing for publication, try to use spelled-out numbers at the beginning of a sentence in place of numerals. This distinction is not based on grammar, but rather the conventions of academic writing in English.

  • 15 samples were collected” should be written as “Fifteen samples were collected
  • At times, writing out the numeral at the beginning of the sentence would be particularly unwieldy. In such cases, it is preferable to rearrange the sentence such that the numeral is not placed at the beginning. For example, “6579 patient charts were collected for analysis” could be altered to “Charts from 6579 patients were collected for analysis
  • Note that some chemical compounds include numerals, and these should not be written out, even at the beginning of a sentence: “5-hydroxytryptamine is a neurotransmitter derived from tryptophan.

Be consistent in the use of numerals or spelled-out numbers

Other tips for number usage involve consistency within your manuscript. As shown above, each number can be written as a numeral or a word. Many authors choose to use numerals for large numbers (say, those over 10) but words for small numbers. Either form is typically fine, but it is best to be consistent with your choice.

  • If “We collected a total of eight samples” is written in your Methods section, avoid writing “Samples from all 8 lakes were nearly identical in pH” in your Results. Either correct the first sentence to include a numeral (‘8’) or change the second to the spelled-out word ‘eight.’
  • In addition, try to avoid mixing numerals and spelled-out words within a single sentence. For example, we suggest changing “The zoo has two pandas, eight elephants, and 15 orangutans” to “The zoo has two pandas, eight elephants, and fifteen orangutans.”

Other tips for consistency with numerals

Here are two other ways to make sure that your numerals are consistent within your manuscript. Consistency in your formatting choices is one way to demonstrate your attention to detail. Always consult your target journal’s style sheet to see what they prefer.

  • When using numbers larger than 1000, be sure to format them all in the same way. For example, 156000, 156,000, and 156 000 are all acceptable, but use only one format in your document.
  • Be consistent with the inclusion or omission of a leading zero before decimals (i.e., 0.05 or .05, but not both). Also, do not mix the use of a decimal point (0.12) with a decimal comma (0,12). In the vast majority of cases, journals prefer the use of the decimal point.

We hope that this article provides some guidance for the use of numbers in your writing. If you have specific questions about the numbers in your text, write to us by email at [email protected]. As always, AJE wishes you the best of luck with your research and publication!

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