If all you're interested in is "Scales" well... That's a very complex subject, in Poser. In general, you model for the scale of the "figure", depending on who created it and what version of Poser it was originally created for... and stuff. See here: http://www.morphography.uk.vu/scaleobj.html

In Poser's options menu, you can select the units of measurement that are displayed in Poser's various windows/tools. However, that does not necessarily mean that Poser accepts objects exported from other applications at that same scale - Poser objects are outrageously tiny little things relative to other 3D applications. "Scale" compatibility issues have always been a problem for Poser. Yes, that means for 3D artists used to scales being absolute, there will be a problem... :)

In general, for use in other applications, most people recommend that you import Poser figures at a scale of 500 into whatever application you're using and then export them at .002 once you have created whatever elements or morphs you wanted to make.

Fireangel's tools are fairly accurate general measuring tools and they are free: http://www.sharecg.com/v/40765/browse/11/Poser/Poser-height-measuring-rulers Also, this is an accurate tool for measuring circumference and it can be adjusted, depending upon the figures that you are measuring: https://www.renderosity.com/mod/freestuff/?item_id=73717 There is also a good product by the above vendor that you can get for the general measuring of body parts and the like, for custom-morphing to real-world dimensions. But, you really don't need much of anything other than that freebie circumference tool for that.