Sometimes a cozy memory foam mattress doesn’t fit where you’re trying to put it or not to have another reason to alter its size. Regardless, you’ll need to know how to go about cutting it. What is the best way to cut a memory foam mattress?

The best way to cut a memory foam mattress is to first gather your material and tools, then to mark lines on the foam where you’re going to cut. Using a suitable technique for your blade of choice, make precise cuts. When you’re finished, trim any excess material or jagged edges.

In this article, I’ll be covering the possible reasons you may wish to divide a memory foam mattress into smaller pieces, as well as what steps you need to take actually to do it.

Is It OK to Cut a Memory Foam Mattress?

It’s perfectly fine to cut a memory foam mattress. You’ll just have to know exactly how much you want to cut off because you want to get your cut right the first time without dealing with the hassle of spray adhesive.

There are many reasons you might want to cut your memory foam mattress to adjust its size. Some of those reasons include:

  • To put it on a smaller box spring
  • To use on a custom base
  • To customize for an unusual area, like a van home
  • To split one big mattress into two smaller mattresses
  • To use the excess memory foam for padding, pillows, craft projects, or other purposes

What Knife Should I Use to Cut Memory Foam?

The knife you use to cut your memory foam mattress will determine how clean your cut is and how difficult it will be to make the cuts. Different types of knives will call for different cutting techniques as well.

Electric Knife

These knives typically have serrated edges and are very easy to use: it’s just two very thin edges with a motor that makes them vibrate. You probably only have to slide the knife along your cut lines to come out with very clean and defined cuts for cutting foam.

Carving Knife

Carving knives usually have serrated edges and are like an electric knife that lacks a motor. The serrated edges cut well through foam but tend to make ragged cuts that you’ll need to clean up later. Use this knife with very short back-and-forth movements for the best effect.

Horizontal Saw

This type of saw should only be used if you’re going to cut the mattress horizontally. With that kind of cut, you have to hold the mattress still as you cut without putting weight on it. Otherwise, you may cause it to warp or compress.

Heavy-Duty Large Scissors

Extra-large or heavy-duty scissors are a great choice for cutting thin memory foam mattresses or memory foam mattress toppers, as long as they fit within the scissors’ jaws. To keep cuts as straight as possible with these, cut a little bit at a time along your cut line. Overdoing it with a single cut can make your cut veer.

Utility Razor Knife

Utility razor knives are awesome at cutting memory foam because they literally use a razor blade. Unlike a carving knife, these have smooth blade edges and are cut differently. To use a razor knife for cutting memory foam, make an initial cut along the cut line and continue deepening the cut with successive passes until you cut all the way through.

How to Cut a Memory Foam Mattress

Now that you know what knife you’ll use, it’s time to outline your desired cuts and actually make the cuts to your memory foam mattress. Depending on your blade of choice, some trimming afterward may be necessary.

Gather Materials and Tools

In addition to your memory foam, you’ll need a few other objects to make the process as easy and painless as possible.

Here’s what you’ll need:

  • Knife of choice
  • Plywood or drywall square to use as a straight edge
  • Safety glasses/goggles
  • Marker or marking pen
  • Tape measure
  • Ruler
  • Spray adhesive (optional, but you’ll need it if you want to glue pieces together)

Determine Dimensions and Mark Cutting Lines

Before you start cutting, you have to figure out the exact dimensions you need. If you’re just cutting the mattress in half, this is irrelevant for you. But if you’re custom-fitting the mattress into a specific area, like a boat or van, you’ll want to pay close attention.

Use your tape measure to determine the dimensions, then use the marker to outline where you’ll be making the cut. A clear outline will make it much easier to know what you’re doing.

Remember to consider all three dimensions when doing this, and mark any slants you may need to factor into your outline and resulting cut.

When measuring, add 1/8th of an inch (3.17 mm) to the marks. This is where you’ll cut; the extra space is for the material that’ll be shaved off and lost when you cut. This extra bit is just to make sure you make accurate cuts.

When dealing with very thick memory foam mattresses, you may need to make outlines on both sides. This is because cutting from only one side may not cut all the way through evenly. I’d recommend cutting about halfway through on the first side when cutting a thick memory foam mattress, then flipping it to finish the cut.

Take care to not put any weight on the mattress when doing this step because it can throw your measurements off: a single misplaced line can make the whole outline wrong.

Make the Cuts

Place your memory foam mattress on a large, flat table or a perfectly even area on the ground. Put something heavy on the area you aren’t cutting to hold the mattress in place – you want it away from your initial cut, so it doesn’t compress the foam and throw your cut off.

Hold your knife directly perpendicular to your initial cutting line and cut. Different knives, as described above, will call for different techniques.

No matter the knife, though, do not put pressure as you cut. This will warp the foam and throw your cut off. If you mess up and need to glue something back on, you can optionally glue it back on with spray adhesive.

For thick memory foam mattresses, you’ll need to utilize the razor knife method no matter the knife: make an initial shallow cut followed by several light successive cuts. Flipping the mattress and making cuts on that side may be necessary, depending on your outline.

Your mattress may have multiple foam layers of differing thicknesses. In some mattresses, the bottom is much thicker than the top. Be aware of this if your mattress is like that because the thick layers are harder to cut. Ironically, they’re simpler to cut because the light layers tend to warp as you cut.

Trim Excess Material

Depending on the exact consistency of your memory foam mattress and the type of knife you used, the edges of your cuts may not be very clean. In fact, they’re probably kind of ragged. That’s okay, though, because it’s pretty easy to clean them up. Just take a pair of scissors or a razor knife and trim the edges of the cuts to even them out.

You may opt not to trim the excess, especially if you’re going to be covering it with a fabric cover or mattress protector anyway. You can throw away the excess foam, or you can keep it; loose memory foam is great for stuffing pillows.

Final Thoughts

Memory foam mattresses are extremely comfortable and even customizable with the help of some careful planning and a good blade. With just a few simple steps and a keen eye, it’s easy to cut a memory foam mattress.

Related: How to Soften Your Memory Foam Pillow

Write A Comment