How to Cut a Foam Mattress

Melissa Lewis

Mattresses are made from various materials, including foam, which many people find extremely comfortable to sleep on. However, you may need to cut your foam mattress to fit onto a smaller bed, or if the foam is thin, you may be using it to make something new like seat cushions or padding for a headboard.

Cut a Foam Mattress

Without purchasing expensive cutting tools, there are a few tricks to get the job done like a professional with everyday household objects.


You can often get electric kitchen knives at garage sales or secondhand stores. Perform a practice cut on the outsides of your lines first. Double check your measurements before you cut.


Cutting your foam mattress will breach any warranty you may have.

  1. Lay the foam mattress onto the floor. Place large pieces of cardboard under the areas where you will be cutting.

  2. Measure and draw lines on your mattress. Use a marker to place a dot every 18 to 24 inches where you plan to cut. Use a yardstick to draw straight lines from dot to dot. If it is a curved line, you should make a template with cardboard, paper or fabric first and then lay it on top of the foam and trace along the edges.

  3. Use a serrated electric kitchen knife to cut. Hold the electric knife straight up so that it is at a right angle to the foam. Cut straight along your lines. Spray the blades with silicone if the knife gets too slow.

  4. Tear or cut any foam that is still slightly attached at the bottom of your cut. It may tear right off, or you may need to use a pair of scissors to separate.