Editing Preferred number (section)

{{short description|Standard guidelines for choosing exact product dimensions within a given set of constraints}}
{{Use dmy dates|date=May 2019|cs1-dates=y}}
{{Use British English Oxford spelling|date=December 2011}}
In [[industrial design]], '''preferred numbers''' (also called '''preferred values''' or '''preferred series''') are standard [[guideline]]s for choosing exact product dimensions within a given set of constraints. 
Product developers must choose numerous lengths, distances, diameters, volumes, and other characteristic [[quantities]]. While all of these choices are constrained by considerations of functionality, usability, compatibility, safety or cost, there usually remains considerable leeway in the ''exact'' choice for many dimensions.

Preferred numbers serve two purposes:
# Using them increases the probability of compatibility between objects designed at different times by different people. In other words, it is one tactic among many in [[standardization]], whether within a company or within an industry, and it is usually desirable in industrial contexts (unless the goal is [[vendor lock-in]] or [[planned obsolescence]])
# They are chosen such that when a product is manufactured in many different sizes, these will end up roughly equally spaced on a [[logarithmic scale]]. They therefore help to minimize the number of different sizes that need to be manufactured or kept in stock.

Preferred numbers represent preferences of simple numbers (such as 1, 2, and 5) multiplied by the powers of a convenient basis, usually 10.<ref name="GOVPUB-C13"/>
[[File:preferred_numbers.svg|thumb|Comparison of preferred numbers of the 1-2-5, Renard and f-stop series on a logarithmic scale divided into 40 equal intervals (blue)]]