upholstery foam 4 x 21 x 78
Need a long, slim cushion that holds its shape? Upholstery foam 4 x 21 x 78 is a practical precut size for bench seats, window seats, daybeds and other long seating where a standard chair cushion just won't stretch far enough. At 4 inches thick, it offers real comfort without looking bulky, and the 21 x 78 footprint suits many built-in benches and narrow platforms.
Where a 4 x 21 x 78 Foam Cushion Fits
- Window seats and breakfast nooks that need one continuous cushion
- Entryway and storage benches
- Daybeds, camper bunks and boat seating
- Replacement foam for worn-out, flattened cushions
What to Look For
Density and Firmness
High density foam generally keeps its shape longer under daily use, while firmness determines how the seat feels. Choose firmer foam for upright seating and softer foam for lounging.
Measure Before You Buy
Measure your seat frame carefully and decide whether you want a snug fit or a little extra room for batting and your cover fabric. A layer of batting softens edges and helps fabric fill out neatly.
Find Your Foam
Ready to build or refresh your cushion? Browse the upholstery foam options below and pick the one that fits your project best.
