I'm making a table where columns are labelled with the property and the units it's measured in:

Length (m)  ||||  Force (N) |||| Safety Factor (unitless)  ||| etc...

I'd like not to write "unitless" on several columns...and I'm quite surprised I can't seem to find a symbol for it. Any suggestions?

Straight from the horse's mouth:


  
  


Source: Bureau International des Poids et Mesures (Search for "dimensionless" for all guidelines.)


  The International Bureau of Weights and Measures (French: Bureau international des poids et mesures), is an international standards organisation, one of three such organisations established to maintain the International System of Units (SI) under the terms of the Metre Convention (Convention du Mètre). The organisation is usually referred to by its French initialism, BIPM.


Wikipedia
