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How to Cut Memory Foam Mattress like a Pro

Have you ever bought a memory foam mattress and realized it’s too large for your bed frame? Or maybe you need to cut it to fit your RV or boat? Whatever the reason, cutting a memory foam mattress can be a daunting task if you don’t know how to do it properly.

Memory foam mattresses have become increasingly popular over the years due to their comfort and support. However, they can be tricky to cut because of their density and thickness. If you’re not careful, you could end up ruining the mattress or injuring yourself.

Cutting a memory foam mattress may seem overwhelming, but with the right tools and techniques, it can be done safely and easily. Whether you want to resize your mattress, create a custom shape or use it for a DIY project, this article will guide you through the necessary steps to achieve a smooth and clean cut. So, let’s get started on how to cut a memory foam mattress like a pro!

Table of Contents

Why Need to Cut Memory Foam Mattress?

Several reasons may require you to cut the memory foam mattress, and they include the following:

  • To get a smaller mattress so that it can fit on a smaller bed.
  • To help accommodate the mattress in a usual area like inside a van or boat.
  • To reuse the mattress for other purposes, like making seat cushions, makeshift pillows, padding for a headboard, and mats.

It is crucial to understand that you must get a clean, clear, and straight cut to avoid any mattress damage.

Valuable Tools You Will Need

You will need sharp and accurate tools to get a clean edge. Blunt or wrong tools will end up making the edges rough and irregular, which with time, they may break down. Below are the valuable tools you will need to cut the memory foam mattress.

  • Electric Knives

Electric knives come with serrated blades. You use them to cut the foam into other odd shapes or when utilizing a template. It would help if you fixed the blade along the memory edge and then cut following your template while using an electric knife.

  • Carving Knives

Just like electric knives, carving knives too have got serrated blades. The blades are crucial in creating a clean edge.

To cut the memory foam, you must only release it shortly alongside gentle back-and-forth movements. Also, do not apply too much pressure when using the carving knives. Moreover, avoid compressing the blade.

  • Heavy-Duty Scissors

Heavy-duty scissors come in handy in helping you cut through thinner portions of the memory foam safely. You can use them to cut through a mattress topper below ¾ inches thick. Remember to apply short chops while cutting and be careful not to cut your fingers.

  • Utility Knives

You can also use utility knives to cut the memory foam because they are surgically sharp. Additionally, these knives differ from serrated knives as they come with smooth edges.

When using these knives, you only have to perform light passes to cut through the foam. You begin by making an initial shallow line, repeat the same process to get a deep cut, and then cut through the foam.

Other tools you will require include:

  • A measuring tape or a ruler for taking measurements
  • A seam ripper, if you cannot remove the mattress cover
  • A sharpie to show the lines through which you will cut the foam mattress
  • A sewing kit for specifically customizing the mattress cover to your new measurements.
  • A plywood or drywall square helps you cut the mattress more precisely and in a straight line.

Meanwhile, you need to ensure you work with caution when cutting the memory foam. Have some gloves and eye and breathing protection. In case of mistakes when cutting, use a spray adhesive made explicitly for your memory foam.

How to Cut a Memory Foam Mattress to Your Desired Size?

Once you have gathered all the valuable tools, you are in an excellent position to start cutting the memory foam mattress. It is vital to note that before you cut the memory foam, you must check whether it contains fiberglass.

If it has and you begin cutting it, the fiberglass particles will scatter all over your room, which may be unsafe. You can read the mattress description online or visit the company from which you bought it to inquire if it contains fiberglass.

Here’s steps about how to cut a memory foam mattress:

remove Mattress Cover

Step 1: Strip off the Mattress Cover

Take out the seam ripper and use it to open the mattress cover if it is attachable.

Step 2: Place the Memory foam on a Flat Surface

If you have plywood, you can use it to protect the floor minimizing the chances of the knife damaging it. Also, if you have a thin mattress, you can use a substantial material on its corners to support it. Ensure the material isn’t heavy for it to break the foam.

Step 3: Determine the Dimensions You Require

mark the Dimensions as Require on foam mattress

After placing the mattress on a flat surface, you must determine the thickness and size of the foam mattress you need. For example, the height should be short if you want to fit the mattress foam on a boat.

You can use a tape measure to check the dimensions you require keenly. Determine the width, height, and depth of the memory foam you need.

When double-checking the measurements, incorporate about 1/8 inch to each size and create marks on the mattress where you will be cutting along.

The excess 1/8-inch is a buffer because some material is lost as you cut the foam. Also, keep the memory foam intact while taking the measurements to increase accuracy.

Memory foam flattens quickly. Therefore, you should put a medium density overlay above the high-density mattress. It helps the foam not to collapse and stay comfortable.

Step 4: Perform the Cuts

The goal is to get clean straight edges. So, to archive this, you will have to set the foam mattress on a solid area, such as the table and the side you are cutting hanging over the edge. The surface should also be sturdy to avoid compressing the cut line.

Then using a cutting tool like the electric carving knife precisely perpendicular to the foam, perform a straight cut using the marks you have made.

Ensure your serrated blade is cutting through the marks you had highlighted. You can use a bread knife if you do not have an electric carving knife.

When cutting, put pressure on the cut line and not the knife. If you use a short blade, you can consider a utility knife where you first make a shallow cut, then rewind the procedure to deepen the cut and eventually cut through the foam.

If your foam mattress is thick, turn the foam to the other side and cut through. Always ensure you make marks on both sides of the memory foam, and they should be equal. You also will discover that the bottom part of the foam has higher density, meaning you will have to apply more pressure to cut through.

Step 5: Trim any Unwanted Material

After you have acquired your desired foam sizes, ensure you trim any excess material remaining. Since you will use a mattress cover, do not worry much about presentation.

You can use a pair of scissors to trim any extra thing. And as simple as that, you will have successfully cut your memory foam mattress.

Step 6: Cover the New Foam with Fabric

You can use your sewing kit to sew a new fabric for the memory form you cut. Alternatively, you can also use safety pins. You tighten the cover against the mattress, fold the remaining material, and pin it. Ensure you do not accidentally puncture the foam.

How to Cut a Memory Foam Mattress Horizontally?

Cutting your memory foam mattress horizontally serves as a great way of making it thinner. The process can be complex, but you will achieve it with this guide. You will need special tools and precision. One tool to cut the foam mattress horizontally is a long horizontal saw.

While using it, you must push it through the foam and ensure you hold the top part of the mattress but do not compress it. You can cover your mattress with a towel and sheet to prevent particles from scattering everywhere while cutting.

Another tool you can use is an electric saw. However, this tool requires you to be alert since it can be risky. A hot wire is another tool, especially if you have a large enough mattress model.

While using a hot wire, you must be steady and avoid distraction while cutting. You can place the mattress in a raised place for easy cutting. Even though cutting the foam horizontally is a great way to get a thinner mattress, it is also a good way of damaging your memory foam.

Additionally, you won’t get a comfortable mattress by cutting it horizontally. Instead, you can opt for a new thinner comfortable foam that will serve you better.


What are some tips to keep in mind when cutting a memory foam mattress?

When cutting a memory foam mattress, it’s important to first measure and mark the area you want to cut with a permanent marker. here are some useful tips for reference.

  • Use a straight edge or ruler to ensure straight lines.
  • Use a bread knife or electric knife with a serrated blade to make the cut.
  • Avoid using scissors or a regular knife as they can damage the foam.
  • Cut slowly and steadily, letting the knife do the work without applying too much pressure.
  • After cutting, be sure to clean any debris from the mattress and let it fully expand before using it. 

How do I Cut up a Memory Foam Mattress for Disposal?

First, make sure you have the right tools on hand, such as a sharp utility knife or an electric carving knife. Then, remove any sheets or covers from the mattress and begin cutting along the seams with the knife. As you progress, shift the mattress to be in a comfortable and safe position, making sure that you avoid cutting yourself or damaging the mattress.

Once you have cut the mattress into manageable pieces, you can dispose of it by taking it to a local solid waste management facility or arranging for a bulk trash pickup. Remember to check your area’s regulations for disposing of large items before proceeding.

Can you cut memory foam with a hot knife?

Yes, you can cut memory foam with a hot knife. Memory foam is a type of foam that is thermoplastic, meaning it can be softened with heat and then molded into different shapes. A hot knife is a tool that produces heat to cut through materials easily.

When cutting memory foam with a hot knife, it is important to use caution since the hot blade can cause burns and the fumes given off by the foam can irritate the eyes and throat. It is also recommended to cut the memory foam in a well-ventilated area and to wear protective clothing, including gloves and eye protection.

Using a hot knife to cut memory foam can create precise cuts and make it easier to complete DIY projects involving this material.

Is it possible to cut a gel memory foam mattress?

It is not recommended unless you have the proper equipment and expertise to do so. Gel memory foam mattresses are typically made with multiple layers of foam, which are cut and bonded to create a specific size and shape.

If you cut the mattress incorrectly, it could affect the structural integrity and support of the mattress, leading to uncomfortable sleep and potentially damaging the mattress beyond repair.

Most manufacturers have strict warranty policies that may become void if the mattress is altered in any way. It is best to leave the cutting of a gel memory foam mattress to the professionals or to purchase a mattress in the desired size and shape.


Cutting a memory foam mattress can be a simple task if done correctly. It’s essential to have the proper tools, take accurate measurements, and use a straight edge to ensure a clean and straight cut.

It’s important to remember that cutting a memory foam mattress may affect its structural integrity. You also need to follow the manufacturer’s recommendations and be mindful of any warranty or guarantee.

With these tips in mind, you can successfully cut your memory foam mattress to the desired size and enjoy a comfortable night’s sleep.

Author: Jessica

Jessica is a lover of both life and gardening. She loves to share his passion for both on social media. He often posts about his latest gardening projects, as well as tips and tricks for others who might be interested in starting their own gardens. She also frequently posts about the different aspects of his life that he enjoys, from spending time with friends and family to exploring new places.

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