Memory Foam for Couch: Firmness, Density and Cut Size

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Quick answer

For replacement couch foam, three numbers matter: the firmness (ILD), the density, and the sheet size you can cut your cushions from. Plan the cut first, then check that the weight on the listing matches the density it claims. In the three foam sheets we read on Amazon on 2026-10-01, only one is actually memory foam; the other two are polyurethane foam, and all three list a firmness of about 44.

We have not tested these products, and every size and rating comes from the listings. For fixing the cover instead, see couch cushion slipcovers. For choosing a new sofa, see sofas and couches.

Memory foam is not the same as upholstery foam

Many sheets sold for couch cushions are polyurethane foam, which springs back quickly. Memory foam is usually described as a slow-recovery foam that molds to the body. The listings use the words loosely. The GoTo Foam and FoamTouch sheets say upholstery foam, with FoamTouch naming polyurethane foam directly. The FoamRush sheet says gel memory foam over a layer of high-density support foam. If you want the slow-molding feel of memory foam, check the material row, not the search term.

A sofa seat needs support more than a mattress does, so a firm base is common. The FoamRush listing describes a ventilated gel memory foam layer on top of a high-density support layer, which is a way of getting some of the memory feel without losing support.

What ILD and density tell you

Two numbers describe foam, and they measure different things. A guide from a mattress retailer defines ILD, indentation load deflection, as the pounds of force needed to compress a foam sample by 25 percent of its thickness over a 50 square inch area. It measures firmness. Its bands are 15 to 21 for soft, 22 to 28 for medium, 29 to 35 for medium-firm and 36 to 50 for firm to very firm.

Density is the weight of the foam in each cubic foot, in pounds per cubic foot. The same guide says it relates to durability: lower-density foam fatigues faster, which causes body impressions over time. The two numbers are independent, so a firm foam can be low density.

The CertiPUR-US program certifies foam for things like low emissions and the absence of certain chemicals such as formaldehyde, but its site does not address durability or comfort. So a CertiPUR-US label tells you about chemistry, not about how long a cushion lasts.

Check the weight against the density

You can test a listing’s density claim with arithmetic. Volume in cubic inches is length times width times thickness; divide by 1,728 to get cubic feet; multiply by the density to get the expected weight.

Worked example.

• GoTo Foam 3 x 24 x 96 in: 3 x 24 x 96 = 6,912 cu in, which is 6,912 / 1,728 = 4.0 cu ft. At the listed density of 1.8, the expected weight is 4.0 x 1.8 = 7.2 lb. The listing says 7.2 lb. They match.
• FoamTouch 2 x 24 x 120 in: 2 x 24 x 120 = 5,760 cu in, or 3.33 cu ft. The listing gives 6 lb and no density, so the implied density is 6 / 3.33 = 1.8. It matches the other sheet.
• FoamRush 3 x 24 x 72 in: 3 x 24 x 72 = 5,184 cu in, or 3.0 cu ft. At the listed density of 1.8, the expected weight is 5.4 lb, but the listing says 6.34 lb, which is 0.94 lb or about 17 percent more. The gel layer or packaging may explain it, but the page does not say.

A weight that matches the claim is a good sign; a gap is a reason to ask.

Plan the cut

Count your cushions and measure each. Worked example with three seat cushions of 24 x 24 inches and a thickness of 3 inches. A 3 x 24 x 72 sheet gives 72 / 24 = 3 cushions, so one sheet covers it with no waste. The 3 x 24 x 96 sheet gives 96 / 24 = 4 cushions, one more than needed, or a spare for a chair.

For a thicker cushion you stack. A 5 inch cushion can be made from a 3 inch sheet and a 2 inch sheet, but then you need two sheets. For three cushions that is 3 x 24 x 72 and 2 x 24 x 72, which cut 3 + 3 pieces. A stacked cushion usually needs a sleeve or a wrap of batting to keep the layers from sliding; the listings do not say, so ask the foam seller.

Measure for the cover too. If the new foam is 1 inch thicker than the old, a snug cover may no longer fit; compare with the ranges in couch cushion slipcovers.

Three foam sheets read on 2026-10-01

GoTo Foam 3″ x 24″ x 96″ 43ILD (Firm) Upholstery Cushion, Made in USA. The table gives a density of 1.8, an ILD of 44, a 96 inch length by 24 inch width and 7.2 lb. The bullets say made in the USA, CertiPUR certified and 43 lb compression. Good for cutting four 24 inch cushions. Keep in mind: it is firm and not memory foam, and the title says 43 ILD while the table says 44.

FoamTouch Upholstery Foam 2″ x 24″ x 120″ High Density Cushion. The table gives polyurethane foam, a 2 x 24 x 120 inch size and 6 lb, and the bullets give a compression rate of 44 lb, a 100 percent recovery rate and a lifespan of 3 to 7 years. Good for the thinnest, longest sheet. Keep in mind: the lifespan figure is the seller’s claim, and the listing says “compress by 1 inch” without explaining it.

FoamRush 3″ x 24″ x 72″ Gel Memory Foam Bench Cushion Replacement, Medium Firm. The table gives a gel memory foam fill, a 72 x 24 inch size and 6.34 lb, and the bullets give a density of 1.8 and a compression of 44 ILD with a ventilated gel layer and a support layer, certified by CertiPUR-US. Good for the only real memory foam of the three. Keep in mind: the title says medium firm while 44 ILD sits in the firm band of the guide above, and the weight does not match the density, as shown.

A full worked example: three 5 inch cushions

Take three seat cushions of 24 by 24 inches, each 5 inches thick. One cushion is 24 x 24 x 5 = 2,880 cu in, and three are 8,640 cu in, or 8,640 / 1,728 = 5.0 cu ft. A 3 inch sheet of 24 x 72 inches is 3.0 cu ft and a 2 inch sheet of the same size is 2.0 cu ft, so together they supply exactly 5.0 cu ft. At the listed density of 1.8 lb per cu ft, 5.0 cu ft of foam weighs about 5.0 x 1.8 = 9.0 lb.

That means two sheets, 3 inches and 2 inches thick, cut into three 24 inch pieces each, make three 5 inch cushions with no waste. You would then stack a 3 inch piece and a 2 inch piece for each cushion. If you buy the 3 x 24 x 96 sheet instead, the extra 24 inches is a spare piece for another cushion or a chair seat.

Questions to send the seller

• Is this memory foam or polyurethane foam, and what is the density?
• What is the ILD at 25 percent compression, and how was it measured?
• Is the foam CertiPUR-US certified for the exact product I am buying?
• Can the sheet be cut to a different size, and what is the tolerance?
• What is the return policy for cut foam?

How to choose

1. Measure every cushion and add the thickness you want.
2. Plan the cut from a sheet size, and check for waste.
3. Pick firmness: 44 is firm; choose a lower number for a softer seat.
4. Check the weight against the density as in the sum above.
5. Check the CertiPUR-US label for chemistry, and do not treat it as a durability claim.

You may not need to replace the foam. If the cover is the problem, a new cover is cheaper and quicker; if only one cushion is flat, replace just that one.

Mistakes to avoid

• Buying by the word “memory”. Read the material row.
• Ignoring thickness. A cushion that is 1 inch thinner feels very different.
• Treating a certification as a durability claim.
• Forgetting the cover. New foam may not fit an old cover.
• Not planning the cut. A sheet that is 2 inches short wastes the purchase.

Bottom line

Plan the cut, check the firmness and density, and test the weight arithmetic before you buy. If the listing’s weight does not match its density, ask. For a worn cover rather than worn foam, see couch cushion slipcovers.

Frequently asked questions

What ILD should I choose for couch foam?

A mattress retailer’s guide puts 22 to 28 as medium, 29 to 35 as medium-firm and 36 to 50 as firm. The three sheets above list about 44, which is firm. Pick the band you prefer.

What is foam density?

It is the weight of foam in pounds per cubic foot. The same guide says it relates to durability, while ILD relates to firmness.

Is memory foam good for couch cushions?

It can be, but memory foam is soft and slow, so many cushions use a firm base under it. The FoamRush sheet pairs a gel memory foam layer with a high-density support layer.

Does CertiPUR-US mean the foam lasts longer?

No. The program covers chemical content and low emissions and does not address durability or comfort.

How do I cut foam for a couch cushion?

Measure the old cushion, mark the shape on the new foam and cut slightly oversize. The listings do not give cutting instructions, so follow the foam seller’s advice.

Products worth checking

We have not tested these products. Sizes and features come from the Amazon listings, checked on September 30, 2026; where a listing does not say, we say so.

Sources checked

• Mattress Miracle: ILD vs foam density guide
• CertiPUR-US

Specifications checked on September 30, 2026. Product details and availability can change, so confirm on the product page before you buy.