How Thick Should a Futon Mattress Be?

Depth by use case

The jump that matters is from six to eight inches, and it is not linear. Six inches of foam under a side-sleeping adult is firm with the hip close to bottoming out; eight inches of pocket coil lets the hip travel two or three inches and still has material underneath. That is why the 8-inch band is where “a futon you can actually live on” starts.

Going the other way, the honest thing about four inches is that it is a storage decision rather than a comfort one. A MAXYOYO floor futon at 4 inches is 10 to 14.5 lb and rolls away to nothing, which no other guest bed does. You buy it for the 355 nights it is not in use.

The frame overrides your preference

Check this before you shop for a mattress. Several frames publish a hard ceiling, and on some of them exceeding it breaks the mechanism rather than just looking wrong.

On a pop-up trundle the limit is structural. The point of a pop-up is that the trundle rises level with the daybed to make one continuous surface; put a thicker mattress on one of the two beds and they stop meeting. That is the whole feature gone, and it is why the two frames on that list which publish nothing are a genuine problem for this format.

On a wall bed, the limit is about the lift mechanism rather than the fit, and there is a minimum as well as a maximum. Bestar’s queens specify 60 to 90 lb because the bed is counterweighted for a mattress in that band. The reasoning is in how much weight a Murphy bed holds.

Construction, once you have fixed the depth

Two mattresses at eight inches are not the same mattress. Having chosen a depth, the next question is whether the material compresses locally or as a region.

Independently encased pocket coils compress in small local clusters. Put a hip on them and a few coils go down while the ones under your waist stay up, which dishes the surface. The DHP 8-inch uses 15-gauge coils with foam and polyester layers, at 75 by 54 inches — standard full. It is the closest a drop-in futon mattress gets to a real bed.

Foam compresses across a region, pulling neighboring material down with it. Memory foam does this better than ordinary polyurethane because it creeps to shape. It also folds and stores better than coils: the Milliard 6-inch tri-fold is 75 by 31 by 6 inches flat and 31 by 25 by 18 inches folded, with 1.5 inches of 3 lb memory foam over a 4.5-inch base, and it goes in a closet.

Weight is the hidden cost of depth. The 8-inch coil mattress is 59 lb net. That is stiff to bi-fold the first dozen times and a light tube-steel frame will feel it. Check what your frame is rated to carry before putting eight inches of pocket coil on it. The full category comparison is in the best futon mattresses.

Adding depth to what you already own

If the mattress is already bought and it is too thin, total depth is still what matters and a topper adds it. Three inches over a four-inch pad is seven inches of material, which beats a five-inch mattress described as plush.

One hard constraint decides which topper: two inches folds into a sofa-bed cavity along with the mattress and can stay there permanently. Three inches will not, so it has to come off and be stored between guests. On a guest bed that distinction matters more than comfort, because a topper that lives in a closet is a topper that does not get used.

And the exception to all of this: a split-back convertible sofa has no separate mattress at all. The sleeping surface is the upholstery, with a structural seam across it, so a loose topper slides apart along the fold overnight. On a sofa, the only figure worth comparing is the open sleep height — 15 to 17.5 inches across the models we cover. The workarounds are in how to make a futon more comfortable, and the depth-by-sleeping-position detail is in the best futons for side sleepers.