I have excellent news for you, whether you want to reuse your old memory foam mattress or need to attain precise dimensions:

A memory foam mattress may be readily sliced at home using equipment you presumably already have.

So, let’s see how to adapt your old foam mattress to new proportions and make it completely meet your demands.

What Knife Is Best for Cutting Memory Foam Mattresses?

When it comes to memory foam, it is a very flexible substance.

As a result, you won’t require any heavy-duty equipment.

A knife would suffice, but not just any knife.

The following are the most frequent varieties of memory foam mattress cuts:

  • Knife with electricity this is perhaps the most straightforward. You’ll save time and work by simply sliding the knife through the foam. Furthermore, utilizing an electric knife produces the sharpest, cleanest edges.
  • Knife for carving. Also useful is a long, sharp carving knife. To cut through the foam with this knife, you must make quick back and forth strokes.
  • Knife for crafts (utility). These knives are usually sharp enough to cut through foam. They also frequently have a sharp tip that makes going through the material easier. However, you should avoid sawing movements in this instance. Instead, start with a shallow incision on a tiny piece of foam and progressively deepen the cut until you reach the bottom and cut through it. You may then go to the next phase.
  • Scissors, extra-large. You may also use heavy-duty scissors if you don’t have an appropriate knife (or if yours isn’t sharp enough). For a smoother finish, cut smaller pieces of foam and use just the tip of the scissors (and more precision).
  • Long bread knife with serrations. A bread knife, if sharp enough, may readily cut through memory foam. To cut through the material, you’ll have to employ sawing movements. The edges may get ragged, but this shouldn’t be a problem if you want to cover your mattress with cloth.

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Other Resources You’ll Need

So, if you’ve invested in the greatest memory foam mattress and don’t want to part with it, a few easy tools may help you turn it into something new (like an RV mattress, for example).

Here’s what you may require:

  • a ruler or a measuring tape (for taking measurements);
  • a sharpie (to indicate the lines along which your foam mattress will be cut);
  • a seam ripper (if the mattress cover cannot be removed);
  • a sewing kit (for customizing the mattress cover to the new measurements);
  • a drywall square or a plywood/hardboard piece (to help you cut the mattress in a straight line and be more precise).

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Cut a Memory Foam Mattress to the Size You Want

You may now begin cutting your mattress after you have all of your equipment set.

Before we begin, a word of caution: if you wish to cut a memory foam mattress, you must first determine if it includes fiberglass.

If it does, the fiberglass particles will be ejected into the room as you begin cutting.

And, to say the least, this might have extremely unpleasant repercussions (which may even harm your health).

Read the description online or contact the firm where you purchased your mattress to find out whether it includes fiberglass.

If you discover that your mattress contains fiberglass, cutting it is not an option.

Perhaps you’d want to investigate one of the finest memory foam mattresses without fiberglass in the future.

If you decide to trim your mattress, these are the measures you should take:

  • Remove the mattress cover. Use the seam ripper to “open” your mattress if it isn’t detachable.
  • Make sure your mattress is on a solid surface. You can protect your floor with a piece of plywood below in case your knife destroys it. If your mattress is thin and light, you may want to anchor it in place by placing something substantial on the corners (like a couple of books, for example). They don’t have to be very heavy (to avoid breaking the foam), just hefty enough to keep the mattress from slipping off the bed.
  • Determine the measurements of the mattress you want, measure it, note the size, and use a sharpie or a marker pen to draw the lines according to the new dimensions;
  • Without compressing the foam, cut the mattress. Keep in mind that the foam at the bottom may have a greater density, so you may have to exert a little more effort to reach it. When working with softer foams, it’s also a good idea to add a drywall square (or a piece of plywood) to keep the mattress from warping.
  • If the foam edges turned out to be ragged, trim away the excess. A pair of scissors or a tiny knife will suffice;
  • Fabric should be used to cover your “new” mattress. That’s when your sewing gear will be useful. You may also use safety pins if you don’t want to sew. Simply pull the cover close against the mattress, fold the extra fabric in half, and pin everything together (being careful not to puncture the foam).

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How to Horizontally Cut a Memory Foam Mattress

You may cut your memory foam mattress horizontally if you need to make it thinner.

Allow me to preemptively tell you that cutting a foam mattress horizontally may be challenging.

Precision and, of course, specialized tools are required.

You now have many alternatives.

A long horizontal saw is the most popular.

While carefully pushing the saw through the material, make sure you grip the top piece of the foam but don’t press too hard on it.

Because some foam particles may fly about, it’s a good idea to cover your mattress with a sheet or towel.

The cloth under the mattress will trap them, making your cleaning job much simpler.

You can also use an electric saw if you have one, according to some users.

However, since it may be risky, I feel it is best to stick to a standard one.

You might be wounded while using an electric saw, particularly if you attempt to grip the top piece of the mattress to keep it from slipping off while cutting.

In this scenario, a normal saw is much safer.

A hot wire is another alternative (if you manage to find a wide enough model for your mattress).

Keep in mind that this technique requires a very steady hand.

Also, if you lay the mattress on a higher platform, you may find it easier to cut it.

Having said that, I would not propose cutting your mattress horizontally.

It’s the most straightforward approach to ruin the foam.

Furthermore, there’s no assurance that your “new” mattress will be comfortable enough.

Instead, you should consider purchasing a new one.

For example, among the greatest memory foam mattresses according to Reddit users, I’m confident you’ll discover a suitable thickness selection.

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Is cutting memory foam permissible?

Yes, as long as you treat it gently, it should be OK. 
To avoid ruining the texture of the material, try not to compress it or use too much power while using the knife.

Can you use a hot knife to cut memory foam?

In theory, yes, but using a hot knife might harm the foam and cause it to lose its form. 
A standard knife will suffice if it is sharp enough; there is no need to use a heated knife.

Is it possible to cut a gel memory foam mattress?

Because the gel particles are embedded with foam, you won’t have to worry about gel leaking throughout the cutting process.

How To Cut Foam Mattress Videos Suggestions From Youtube

Cutting a Foam Mattress in Half – Lefie
How to cut memory foam – Make & Do
RV bed revisited. How to cut foam with a carving knife. – Xplorer Steve DIY


Who says a custom-size memory foam mattress can’t be made at home?

All you’ll need is a good knife and a ruler.

And, certainly, some time.

However, as a consequence, you may purchase almost any mattress size you wish.

Just be cautious not to compress the foam too much throughout the procedure.

After all, you’ll want your “new” mattress to keep its qualities.

What is the purpose of cutting your memory foam mattress?

Are you attempting to reach any certain size or shape?

Please share your thoughts in the comments box below!

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Written by Bob Matsuoka
Bob Matsuoka is a blogger and founder of RVing Beginner blog. He has been blogging for over five years, writing about his own family’s RV adventures, tips for people who are interested in buying an RV or taking their family on an adventure by RV.