Usually I render at wallpaper size, 1920x1200 for laptop, 2560x1600 for workstation, or occasionally double width 5120x1600 for laying across an extended desktop (two monitors).

     Sometimes for demo/test renders, I aim for a size suitable for posting in the forum.

     For animations, I generally use 720x480 (DVD widescreen) or 640x480 (DVD standard TV), but I may render smaller if the animation is especially processor-intensive or a lot of frames.

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5