Editing Tip: Formatting Compound SI Units

Different authors and different journals utilize different spacing and separations for SI units. When writing out units, a hyphen (-) or a space is usually used between the words to represent multiplication (as in newton-meter or newton meter). The word per is used to represent division (e.g., newton per meter).

When writing products of SI symbols, there are several accepted conventions:

• Nm - no space between the SI symbols
• N m - one space between the SI symbols
• N*m, Nxm, N x m, N·m, or N.m - a symbol representing multiplication between the SI symbols

Note that combinations of same units should always use exponents to avoid confusion (e.g., m*m should be written as m2).

When an SI symbol is being divided by another, there are two main accepted conventions:

• N/m - a solidus between the SI symbols to indicate division
• Nm-1 - a negative exponential to indicate the SI symbol in the denominator
  In this case, any of the conventions listed above for the products of SI symbols can be used

We hope that today's tip has helped clear up how to describe SI units in a research paper. Please email us at [email protected] for more information. Best of luck with your writing!