Sofa Cushion Filling: What Works, What Doesn't, and How to Choose

When you sit down on a sofa, what you feel isn’t just the frame or the fabric—it’s the sofa cushion filling, the material inside the seat and back cushions that determines comfort, support, and lifespan. Also known as cushion core, it’s the hidden hero—or the silent failure—of your favorite seating.

Not all fillings are the same. High-density foam, a firm, resilient material rated by pounds per cubic foot lasts longer and holds its shape better than cheap, low-density foam that turns to mush in a year. Then there’s down filling, soft clusters from duck or goose feathers that offer a plush, sink-in feel, often mixed with foam for support. And polyester fiber, a budget-friendly synthetic option that’s easy to clean but flattens faster, is common in lower-priced sofas. Each type has trade-offs: foam gives structure, down gives luxury, fiber gives affordability—but none last forever.

Why does this matter? Because replacing sofa cushions isn’t cheap, and buying a new sofa just because the filling collapsed is a waste. Most people don’t realize that cushion density (measured in pounds per cubic foot) is the biggest predictor of durability. A 1.8 lb/ft³ foam lasts about 3–5 years. A 2.5 lb/ft³ foam? It can last a decade. Down blends feel amazing but need fluffing and may trigger allergies. Polyester fiber is soft at first but loses loft quickly—especially under heavy use. And if your cushions are sagging, it’s rarely the fabric’s fault. It’s the filling.

You don’t need to be an expert to pick the right one. Just know this: if you sit for hours, go for foam with a higher density. If you want that cloud-like feel and don’t mind maintenance, mix down with foam. If you’re on a tight budget and have light use, fiber works—but expect to replace it sooner. And if you’re thinking about reupholstering, don’t just swap the cover. Replace the filling too. It’s the difference between a sofa that feels new and one that feels like a memory.

The posts below cover everything from how to tell when your filling has given up, to what professionals use in high-end furniture, to simple fixes you can do yourself. Whether you’re trying to revive an old sofa or choosing a new one, you’ll find real, no-fluff advice here—no marketing jargon, just what actually works.