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SOP Writing: How To Number Procedures Correctly


When writing procedures, should you write one or 1?

It’s a small detail but how you use numbers in SOPs influences how others interpret your instructions and perform tasks correctly. In some situations, you should use one whereas in others 1 is the correct word to use. So, which one should you use? And where?

Let’s look at four ways you can write numbers correctly and also some mistakes to avoid.

Standard Operating Procedures (SOP) Template

Adding Numerical Information to SOPs

Unlike other types of documents, you need to be very exact when providing information in procedure manuals.

After all, the person using the manual may be in an emergency situation, struggling to install an application, and under stress. You don’t want to compound the problem by writing vague or ambiguous text.

Here’s how to write clear instructions when you need to provide numerical information.

1. Using spelled-out numbers

In this example, we look at when to use a ‘spelled out’ number, for example, two instead of 2.

Here’s the rule:

Use spelled-out numbers when one number – WITHOUT a specified unit of measure – is followed by one WITH a unit of measure.

For example:

Use: “Turn on one 3.25 kV bus.”

Do not use: “Turn on 1 3.25 kV bus.”

In the second example, it’s hard to tell if it’s one 3.25 or 13.25. The first example is much easier to read. It’s the 3.25 kV bus you need to turn on, right?

2. Use of spelled-out numbers with emphasis.

Along the same lines, use spelled-out numbers when a number, typically a single digit number, is


“Use one of the following:”


“Use 1 of the following:”

In the second example, the use of 1 feels incorrect. The problem here is that, although the information is technical valid, the reader will slow down and possible re-read this section.

“Why do they say, ‘Use 1…’ ”

3. Use Arabic numbers to present numerical information

In the final example, this construction

“Reduce speed by 10 kilometers.”

Is preferred to:

“Reduce speed by ten kilometers.”

In the first example, the number 10 is stands out from the text and highlights to the readers, ‘Look, you need to slow down by 10 kilometers.’

In the second example, it doesn’t have the same affect.

4. Consistency

Be consistent when using Arabic numbers (e.g., 0, 1, 2, 3) and spelled-out numbers (e.g., zero, one, two, three). Don’t get ‘creative’ and start changing the numbering system throughout the document.


Help the reader become familiar with your writing style and format. Don’t spring surprises!

One way to do this when writing procedures is to remove any possible misunderstanding from your instructions. In other words, look at the numbering systems you’re using and ask yourself if the person reading this could be confused by the way you’re written it.

If the numbers could be misunderstood, then revise the text and use numbers that clarify how the process works.