First swing cushion set I ordered? Way too small. Looked fine in the photo. The listing said "fits most swings." It sagged in the middle, slid when I sat down, and after one summer the fabric faded to a weird pink.
Second set? Better size, but I forgot to check the depth. The cushion hung off the back by three inches. My head hit the frame. Dumb mistake.
Here's what I wish someone told me before I wasted two returns.
Measure the seat, not the swing
Most people measure the swing's width. That's half the job. You also need the depth (front to back) and the back height.
I used a tape measure and wrote it down. Width of the seat frame? 48 inches. Depth? 18. Back height? 17. My first cushion was 46 wide and 14 deep. No wonder it slipped.
The cushion should sit snug, not float. If it's too small, it shifts. If it's too big, it won't lie flat. Aim for no more than an inch of play.
Also check the ties. Most sets come with two or four. My swing had three spots to tie. Guess what? I ordered a set with two. Pain in the rear.
Check the fill before you buy
Polyester fill is cheap and clumps fast. Foam holds shape but can get waterlogged unless the cushion has a waterproof liner.
I didn't pay attention and bought poly. By the end of the season, the seat looked like a lumpy potato sack.
Look for quick-dry foam or at least a removable cover. If you live where it rains, you'll thank me. I store mine in a deck box now, but not after the first soak.
Fabric matters more than color
My first set was a light beige. Pretty in the cart. After two weeks of sun, it looked bleached. Then a bird did what birds do, and the stain stayed forever.
Go with solution-dyed acrylic or polyester with UV protection. It costs more but it actually holds color. Also, darker colors hide dirt. Not that I'm telling you to be lazy. I'm telling you because I'm lazy.
Don't trust the "one size" listings
I've seen swing cushions sold as "fits all swings." That's nonsense. Your swing is built different from the neighbor's. Measure, then order.
If you already have outdoor furniture cushions, check how they fit. The same logic applies. I learned that when I replaced a bench cushion without measuring first. Lesson repeated.
What to do next
Grab a tape measure. Write down your swing's width, depth, and back height. If you have ties, count them. Then start looking. That's it. Measure once, buy once. Don't be me.
More outdoor furniture cushion tips are in that guide. And if you're dealing with a round cushion, here's a separate size warning.