First, start by finding out the inside seat height of your sofa. Please see diagram below for guidance on where to measure. 

Next, add 3 inches to the inside seat height. This will give you your smallest optimal pillow size. 

Then, add 7 inches to the inside seat height. This will give you your largest optimal pillow size*. 

Use this size range to guide your selection of square pillow covers for your sofa. It's ok to layer smaller lumbar pillows in front. 

*Exception: if your sofa has a high back, stick with the smallest optimal pillow size and don't go larger than 24x24.


The inside seat height of the yellow sofa above is 14 inches.

If we add 3 to 14, this gives us 17.

If we add 7 to 14, this gives us 21. 

So, our optimal pillow size range is 17" to 21" squares.

The spotted pillows shown are size 21x21 and the floral pillows shown are size 20x20. 

photos: Natalie Steen