Family Life What is the most popular decorative pillow size? What is the most popular decorative pillow size? The most common throw pillow sizes for sofas are 18″ x 18″ and 20″ x 20″. However, larger sofas and sectionals, especially those with deep seats or high backs, may be better off with 22″ x 22″, or even 24″ x 24″ pillows.Jul 22, 2011 Related Posts:What are these white patches of saliva on my pillow?There is a guide to standard sofa sizes and dimensions.What are mini pillows for?My Pillow Body Pillow Promo Code is updated daily and it is valid for 2999 days.