I like (down or really fluffy) inserts two inches larger so the pillow looks filled out. I think it looks sloppy when the cases are loose on the pillow. So 22" insert for 20" pillow. I did this for all the pillows on my bed and I'm so glad I did.

That said, I think the pillow Justgotabeme posted looks good.

Decorators and pillow manufacturer’s recommend "one size up" for inserts vs. pillow covers, for best fullness. In other words, a 20 x 20" cover would need a 22 x 22” insert. I’ve always followed this guidance, and find that it works best for what I sew.

Thanks everyone! One size up. That's exactly what I needed to know.

Two questions:

1. As luck would have it, my pillows are odd sizes (17x17 and 15x15). If I go with standard, e.g., Pottery Barn, I would have to bump up 3 inches larger, i.e., 20x20 and 18x18. Would that be too much?

2. Anyone used PillowsXpress? They do custom sizes, very inexpensive. Shipping costs more than two pillows. Still cheaper than Pottery Barn with free shipping.

You only need 1" larger for those sizes, especially if you're using feather/down. I'd get an 18x18 and a 16x16. Personally, I don't like an overstuffed, tight looking pillow.

Here is a link to Joann's Fabric http://www.joann.com/search?q=pillowform They have 18x18 and 16x16.

Natesgram

I always use one size larger insert (which is 2 inches) and my pillows don't look "overstuffed or tight". They look nice and full instead of skimpy and flat. A skimpy, flat pillow is one of my pet peeves LOL. That said, I don't think I'd go 3 inches larger.

Thanks all. I just ordered two from Joann's. They're only 1" larger, but on sale and the shipping wasn't bad. If these aren't plump enough for me (and I'm not sure I want them too plump anyway), I can always get customs from PillowsXpress.