Bedding & Bath · Decorative Throw Pillows
What size insert should I use with an 18x18 or 20x20 cover?
Reviewer consensus
The consensus across r/BuyItForLife, r/HomeDecorating, and r/IKEA threads is to size up by two inches—a 20x20 insert in an 18x18 cover, or a 22x22 in a 20x20—so the corners fill out and the pillow doesn't look limp. A minority of reviewers warn that sizing up too aggressively can make the pillow feel rock-hard if you actually lean on it.