How to cut a foam mattress [Ultimate Guide]

Foam mattresses are very popular for their support and variety of firmness options. But there’s always the chance that you might want it in a different size. If you are moving homes or just want to customize the bed for whatever reason, cutting through the memory foam is relatively easy—as long as you know what tools and safety measures to take.

There is not too much useful information on cutting memory foam mattresses so I decided to write this post.

In this guide, I have collected three best methods how to cut a foam mattress. Each of them is optimal depending on your goal.

When and why do you need to cut a foam mattress?

The first question people ask is – why would one even want to cut the mattress itself? There is a relatively big list of situations when cutting a foam mattress would be a better decision that would save money, time, or both.

To transform the shape and dimensions of a foam mattress

For example, you may want to use an old mattress to renovate your sofa or a daybed. The sofa may require a custom size mattresses and the only option would be to cut the foam mattress.

Another example is putting a foam mattress into a chair, RV bed frame, dog bed, back of the van, or put a memory foam topper on your air mattress. All these things would be impossible to do if the mattress couldn’t be cut.

To split a king-sized mattress into two singles

For example, you purchased a new king-sized mattress for you and your spouse. Now you can split your old mattress into two single-size mattresses for your kids. Spending a couple of hours and xx dollars on this is much more reasonable than purchasing a new mattress.

To make a dog bed or other soft flooring for your pet

If you want to create a comfortable place for your furry friend to snuggle up while inside, then cutting foam is an inexpensive way to do so. You can also use this technique to line the bottom of a crate if you don’t want your dog to have a cold, hard floor.

To give a new life to your old foam mattress

With enough creativity, you can make a lot of useful and super-comfortable things by cutting a foam mattress:

  • to make a support pad for a laptop
  • to make a pad to transport fragile parts or objects such as glass or ceramics
  • seat cushions
  • neck pillows for airplanes and cars
  • back cushions for patio chairs and loungers
  • cushion covers to cover a hard surface such as a wicker chair or an antique bench.
  • toppers for ottomans or
  • as support for sleeping bags during camping

To protect your RV mattresses

If you are traveling with pets, especially dogs that like to get under the covers, then you may want to add extra cushioning on top of the mattress. Cutting a foam mattress makes adding an extra layer of foam under the fitted sheet fast and easy.

To make your mattress thinner

For example, you may want your mattress to better fit a foldable sofa, an RV bed, or use it for a cot. To make it thinner, you will have to cut the foam mattress horizontally. In this article, we will show you how to do this.

In addition, the process will not affect the overall quality of your mattress. So do not worry about it not being as comfortable anymore. You can still sleep on it and it won’t change its shape for many years! You’ll be able to enjoy it just as before while saving space and making it fit.

Best tools to cut the memory foam

1. Electric carving knife

An electric knife is not only a very useful device to have in the kitchen but is also a good solution to cut your mattress.

2. Serrated bread knife

If you aren’t afraid of manual work, I advise you to use a bread knife. This is an excellent tool to cut the foam mattress as it is extremely sharp and can be kept clean by wiping it with a damp towel after each use. Its long serrated blade will evenly spread the memory foam along the edge of cutting. Please, don’t make a mistake using the utility knife as its blade is too short and this will result in inaccurate uneven cuts.

3. Hedge clippers

Hedge clippers provide a very good solution to cut memory foam. These heavy duty scissors are lightweight, inexpensive, and easy to maintain. By pressing the top part of the clippers against your foam, you only need to use one hand and it will be enough to keep the mattress in place. As soon as you’ve cut through the foam on one side of the mattress, quickly turn the other side over and repeat the same thing but on this side until you get your desired shape.

4. A hack saw

A hack saw is a great alternative and it is very simple to use. When using a hack saw, you will need to secure the mattress in place but at the same time be able to accommodate the curve of your mattress and keep it steady while you work on it. If your blade starts getting blunted, make sure that you change its direction and continue foam cutting from an angle as it will help preserve the blade. A hack saw makes cuts that are just as fast and even as those made by a saber saw but it requires more skill to operate one without causing any damage to the foam or breaking your hacksaw blade in the process.

5. A saber saw

If you have a saber saw at home, you can use it for cutting the mattress foam but make sure that you clamp your foam down with clamps or some similar securing mechanism. A saber saw is very sharp and goes back and forth really fast. This is why it’s very important that the foam is fixed down so that it doesn’t move during the cutting process or else you could end up with a ripped and messed up mattress.

Additional tools you will need

  • A tape measure (to measure the needed dimensions);
  • a sharpie (to mark the lines along which you are going to cut your foam mattress);
  • a seam ripper (in case the mattress cover is not removable);
  • a sewing kit (to tailor the mattress cover to the new dimensions);
  • a drywall square or a piece of plywood/hardboard (to help you cut the mattress in a straight line and be more precise).
  • u-shaped metal clamps to stabilize the mattress
  • a knife (there is a huge variety of knives on the market that you can use, even an ordinary kitchen knife will do the job. Below you will find the suggestions on the best type of knife)

How to cut a memory foam mattress to the desired shape and size

Caution:

Before getting started, please check if your mattress contains fiberglass. Inhalation of fiberglass particles may lead to various respiratory problems, irritations, or allergies. [1]Effect of fiberglass on health https://www.doh.wa.gov/communityandenvironment/airquality/indoorair/fiberglass

  • Cut a small hole. You can find out if your mattress contains fiberglass by cutting a small hole in the side. If you see a white needle-like substance that is flaking off the mattress, it’s fiberglass.
  • Learn the mattress tag. A mattress tag will help you to make sure you know what size and density your mattress is.
  • Research the information online. You can simply Google, “[your mattress model] materials” to find out if there is any fiberglass in it. You can also check directly the manufacturer’s site and call their customer service.

Step 1. Take off the bedding and a mattress protector.

It is obvious that you should remove the mattress protector and your bedding from your mattress before you cut it.

Step 2. Put the mattress on a flat surface

It is very important to make sure your foam mattress is on a flat surface, without any objects underneath it. Please, use a laser level to make sure the surface is really flat. I suggest you use plywood because it is flat, inexpensive and it will help to protect your floor from any damage caused by a knife or a saw.

Step 3. Tightly stabilize the mattress

Your mattress should be sturdy and not move around easily. This will help you to make a straight cut with your knife or a saw.

You can use any material that acts as a clamp to hold it in place on the plywood. I used some ordinary metal U-shaped brackets. They were cheap and they worked perfectly for me.

Alternatively, you can put the bricks around the mattress. Heavy bricks will prevent your mattress from moving. However, every brick should be wrapped in plastic to prevent your mattress from getting dirty.

Step 4. Draw the cutting lines

Measure your foam mattress with a measuring tape or a ruler and draw a cut line using a pen or marker. Double-check that the line is correct and corresponds to desired dimensions. Do not press too hard while drawing a line because the foam may shrink and the line will be curved.

Step 5. Cut the mattress using a knife or saw

Carefully start cutting from one corner of the mattress and work your way out until you reach the middle of the mattress. Do not rush this step because it is crucial for a good job. You can start with a shallow cut that will direct your instrument towards the cut line and then proceed with the deeper cuts. You should avoid any warping and pressing because it leads to crooked edges.

Tip:

Most modern mattresses have several layers of foam that have different densities. Please, take this fact into account. One layer can be easier to cut than another one. Do not rush when cutting the mattress and make sure you use the right tool. If a knife is not enough to do the job, go for a saw. This way you will be able to give enough support to the blade while cutting through different layers of foam.

Step 6. Cover your mattress with fabric to avoid getting dust or lint

It is important to keep dust, lint, and pet hair off the mattress during the storage period. The foam should not contact with these kinds of dirt. In order to properly protect your mattress, you should pull the covers tight over it and fold the excess fabric. Tuck in one end of the cover into a seam at each side of your mattress.

How to cut a memory foam mattress horizontally

To make your memory foam mattress thinner, you can cut it in half. It is difficult to split a memory foam mattress in half, but it’s manageable with the right tools.

An electric carving knife is the best option here.

Step 1. Start by taking off the sheets featuring any mattress coatings.

You should remove your mattress protector and duvet from the bed before cutting it open.

Step 2. Put the mattress on a plywood sheet

It is important that your mattress is on a flat surface away from other objects. Please use a laser level to make sure your floor is truly flat and lay down plywood underneath the mattress for protection.

Step 3. Put the mattress with plywood on the table

Additionally, this method requires you to put the setup on the table because it should be comfortable enough for you to make straight cuts over and over again.

Step 4. Select the desired side

Your mattress is likely to have several layers of foam with different densities. Please make sure that you picked the right side to be left and then choose the corresponding side while cutting.

Put the denser layer down if you want a firmer mattress and vice versa.

Step 5. Organize a cutting setup

Fix the piece of thick duct tape to a required height. You can use wooden blocks or anything else for this purpose.

Step 6. Start cutting the mattress

Pull the side of your mattress to a cutting setup. Put an electric carving knife on a cutting setup and start cutting the mattress.

The cutting setup will limit the movement of the knife so it always cuts the foam on the same level.

Step 7. Cut off the upper foam using scissors or an electric knife.

The length of your knife is smaller than the length of a mattress. This is why you will have to cut off an upper layer of a mattress, then pull the mattress closer to a cutting setup and repeat steps 6 and 7 one by one until you cut off the upper layer of a mattress.

Step 8: Cover your mattress with fabric to avoid getting dust or lint.

It is important to keep dirt, dust, and pet hair off the mattress during storage. The cover should not contact these kinds of dirt. To properly protect your foam, pull the covers tight over it and fold the excess fabric at each side into a seam. Tuck in one end of the cover into a seam on each side of your mattress.

Please, watch this video to understand the process better

How to cut the memory foam mattress horizontally using a hot nichrome wire

This is the best way to cut memory foam horizontally because the mattress will be cut evenly and the lines will be precise and straight. Also, you may need to cut along the difficult edges and only a hot wire method can lead you to a clean cut.

However, this method is also more difficult for two reasons:

Reason 1: you have to check that your memory foam mattress is not flammable and be extra cautious not to touch the hot wire.

Reason 2: When using this method, you are cutting the foam mattress with a wire that is heated up to 200° C (392F). That requires some skill and experience. And you will have to make your own wire cutter for this.

A hot wire cutter is a tool that works by heating up the length of resistive wire using electricity. The heat of the wire melts the foam and makes it much easier to cut wide sections and intricate shapes.

And you don’t need much to build one:

  • A-frame. I’m using a PVC pipe.
  • Power supply. I’m using this 12-volt power supply
  • Nichrome wire for the heating element
  • Switch, hardware, and wire for the electronics.

Step 1: Make a frame with a PVC pipe

To start, I’m going to make the frame of my cutter, I’m using PVC cement to combine these three lengths of straight pipe together into a C shape using these 90-degree elbows.

I drill the hole in each arm for an eyeball to throw it into. And I use the step drill to make space for a switch.

Step 2: Cut the wire

So I measured out some wire and cut it size. I sat at my switch and protected my joints with some heat shrink tubing. One of the wires from the switch gets fed through the PVC frame and out the other side. And the other gets fed through the bottom and then the switch can be seated in place, I’m using some hot glue to secure mine.

Step 3: Attach a wire to a frame

Next, we’re going to make the points where our hotwire attaches to the frame for you and I will through the hole we drilled in the arm of the cutter and use nuts to clamp the bolt and the wires into place. It would be a much better, much safer plan to have crampon connectors for the wires here. I didn’t have any handy, but I’ll be adding them to my setup. The first chance I get loose wires like this will work, but it is much sketchier than a proper connection.

I sat at the lead for the side of the circuit that goes through the switch around the frame of the cutter, then bolted the other half in place. Then I turn the other ends of my wires. And clamp them into the socket for my power source. The micrometer that we’re using for the cutter will expand as it heats up, introducing slack that will make precise cuts difficult so it can be good to add some tension to the system.

So with the right wire in hand, let’s bring up our country, I attached one end. Then compress the frame and attach the other. Once I release it, the nichrome wire will be nice and tight.

You can watch this video for details:

A video explaining how to cut foam mattress using a hot wire

Step 4: Use a laser level to place the nichrome wire cutter horizontally

Install and fixate the nichrome wire cutter horizontally in front of the mattress laying on the plywood.

Step 5: Start cutting the mattress

Measure the desired thickness of your mattress and mark the lines using a pen. Pull the side of your mattress to a cutting setup. The wire cutter will cut a perfectly straight line as you pull the mattress against it.

Step 6. Cut off the upper foam layer

It may be uncomfortable to pull the whole mattress through the cutter at once. You will have to cut off an upper layer from time to time to make the further process more convenient. A knife or heavy-duty scissors can be used to cut this layer.

Step 8: Cover your mattress with fabric to avoid getting dust or lint.

It is important to keep dirt, dust, and pet hair off the mattress during storage. The cover should not contact these kinds of dirt. To properly protect your foam, pull the covers tight over it and fold the excess fabric at each side into a seam. Tuck in one end of the cover into a seam on each side of your mattress.

Caution:

When you are cutting foam with a hot wire, the heat produced will cause the material to expand and let off toxic fumes which can be harmful to your health. [2]Fire and Combustibility of polyurethane https://polyurethane.americanchemistry.com/Fire-and-Combustibility/

Foam mattress cutting services

Did you know that there is a company called Foamite? This service offers foams that have a different feel to the touch, densities, and different shapes. All you have to do is pick the right density and dimensions.

FOAMBOARD FEETPRICE / BD. FT.COST
103014.67$1.35$19.81
111814.67$1.49$21.86
153014.67$1.95$28.61
157014.67$2.19$32.13
EC3614.67$2.89$42.40
NC3614.67$3.59$52.67
NC6514.67$3.59$52.67
PR2814.67$4.39$64.40
KN3114.67$4.89$71.74
KN5114.67$4.89$71.74

Please, note that they offer a memory foam cut to size instead of cutting your own old mattresses.

Cutting the memory foam pillows

When you cut a pillow, mattress topper, or mattress, the rules are the same. To trim a mattress layer, choose a sharp knife, make straight and precise cuts, and cut off the ends.

When cutting foam, it is most easily cut on a flat surface area and plywood is an optimal option.

In most situations, you’ll want to use the blade level with the density of your foam. Additionally, it’s necessary to practice safety and wear protective equipment when needed. You should refrain from cutting anything longer than the length of your blade because this will require holding open any sections that were previously cut.

Frequently asked questions:

Can you cut a memory foam mattress?

Definitely. As long as the mattress does not contain any fiberglass, it is safe to cut it. I recommend using a gentle touch when using cutlery on scarves to avoid damaging the material. Also please, avoid cutting the flammable foam with a hot wire because this method will cause the material to ignite and burn.

Can you cut memory foam with a hot knife?

Yes, but you should pay attention to the materials of your mattress. If it has any flammable materials, cutting it with a hot knife will make the materials burn, creating a possibility of fire.

Can I cut a gel memory foam mattress?

Yes, it’s possible. The gel particles are infused with foam, so concerns over gelling spilling during the bed-cutting process are avoided.

How to cut thick foam mattresses?

The process is the same. The only difference is that you will have to use a knife, saw, or a pair of scissors with longer blades that will allow you to reach the entire thickness of your mattress.

How to cut memory foam topper?

You can also use this process, but first, disconnect the topper from the bed and lay it out on a flat surface.

How to evenly cut a memory foam mattress?

The best method involves a nichrome hot wire cutter. All you have to do is to build your own cutter and install it sturdily.

Conclusion:

As you can see, there are different methods to cut foam mattresses, so you can choose the one that is most suitable for you. Just pick your weapon and follow these steps and remember to wear all protective clothing when using any sharp tool.

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