How to Easily Cut Open-Cell Foam

DIY projects are all the rage these days, as people realize they’re a smart way to save a few dollars and add a personalized touch to their home. With its versatility and usability, foam is a material that lends itself well to the world of DIY, whether it’s being made into a custom bed mattress, or for replacing an old couch cushion.

As with any DIY project, the most important step is the pre-work prep.  Projects involving foam make this step even more important, and one of the most important things to take care of in advance is making sure you know how to properly cut open-cell foam. Because of its soft and compressible structure, it can be difficult to get clean cuts without knowing the proper techniques and tools to use. Additionally, different foam types need to be handled uniquely when attempting cuts. For example, closed-cell neoprene should be cut in a different way with a different tool than a couch cushion material.

There are two basic ways to cut memory foam and other open-cell foam varieties if you want to achieve the best results, as well as one way to cut that may be tempting but is NOT effective. People occasionally think they’ve discovered a shortcut and squeeze and compress foam to let them cut through quickly. In actuality, this is the last way you should be cutting foam. The foam responds fluidly to pressure as you cut, and when released, leaves you with jagged, uneven edges.

As for the correct ways to cut foam, the easier of the two methods is using an electric carving knife; the same kind used for carving turkey. After carefully measuring and plotting the shape of your cutout on the foam, slowly pass the blade through the uncompressed cushion for easy, straight cuts. When using an electric knife, patience is key, because the slower you go, the cleaner your cuts will wind up.

The other method is slightly more labor-intensive, as it requires manual cutting with a serrated blade. This may sound overly difficult, but is actually very doable and can give you cushions as attractive as those cut with an electric knife. With a gentle sawing motion, start at the edge of the foam without compressing it, and slowly saw back and forth like you’re slicing bread. It’s important to always work on a stable surface that won’t be damaged by cutting. Also, use blades that can fully pass through a foam’s thickness so you don’t end up having to flip the foam and saw from the other side. Knowing these strategies is a key part in the preparation of a DIY cushion and can result in a beautiful final work.