How to Cut Memory Foam Mattress? 5 Easy Steps

by Max Stevens

You might want to know how to cut memory foam mattress for various reasons:

  • You need to reuse your old memory foam mattress to fit a smaller bed
  • You need to split a king memory foam mattress into two
  • You need custom-sized memory foam for a seat cushion or any other reason.

Whatever the case is, I’m sure you’re wondering if it is safe to cut memory foam mattresses. It can be difficult to slice through cleanly, especially if you don’t know the properties of memory foam and if you don’t have the right tools.

Nonetheless, we will share steps to properly cut a memory foam mattress, what tools you’ll need, and takeaway tips to remember.

What is the best tool to cut memory foam?

How do you cut thick foam?

Memory foam mattress ranges from 20 to 30 cm. This thickness is not easy to cut and you risk injuring yourself or damaging the mattress.

In addition, these factors can also make it more difficult to cut through:

  • Mattress firmness
  • Mattress density
  • Number of layers
  • Unique properties of each layer

But with the right tools, cutting memory foam should be pretty easy and straightforward. These tools include:

Judge cutting equipment
Image: Amazon UK
  • Electric knife – This is the best knife for cutting memory foam as it doesn’t take much effort cutting back and forth. As a result, the cut will be sharp and clean. As long as you keep your hand steady, of course.

Sabatier sharp knife
Image: MyChefKnives
  • Kitchen knife – A sharp kitchen knife also works for cutting memory foam if you don’t have an electric knife. Short back and forth motions work well with this knife to cut through memory foam.

Stanley cutting material
Image: Stanley

  • Craft knife – Craft knives are sharp enough to cut through the foam. However, these are short blades only, so you have to make shallow slashes and then get gradually deeper resulting in a not so even cut as well as taking longer.

large gold scissors
Image: Amazon

  • Extra-large scissors – If you don’t have a sharp knife, you can also use large scissors. But similar to using a craft knife, it’ll take a lot longer and be harder.

Other materials you’ll need

  • A ruler or a measuring tape – for measuring the needed dimensions
  • Marker – for drawing lines to aide the cutting process
  • Straight edge cardboard or stick – for outlining

Bed Sizing Guide

Bed size



Small single

190 cm

75 cm


190 cm

90 cm

Small double

190 cm

120 cm


190 cm

135 cm

King size

200 cm

150 cm

Superking size

200 cm

180 cm

illustration of bed sizes with people icon
(Option: illustration of bed sizes similar with BedAdvice)

Before cutting, make sure to double-check the measurements you’re cutting for.

This will help your mattress fit better into standard frames and bedsheets. The table/illustration above can help you outline the bed size.

But if you have a custom bed size, measure this and take note for use later on.

Can a gel memory foam mattress topper be cut?

blue colored gel memory foam mattress
Image source: Recci

If you worry that cutting a gel memory foam mattress can cause the gel to leak, don’t worry.

The gel is already infused in the memory foam.

A traditional memory foam mattress is made of viscoelastic polyurethane, which works by absorbing the body’s heat and using this heat to soften and contour the body.

The microgel beads mixed in with the memory foam help with the heat buildup by absorbing the heat.

Since gel memory foam mattresses are safe from leaking, you can also use the steps discussed previously for cutting gel memory foam mattresses.

What is the best way to cut a memory foam mattress?


  • Cutting your memory foam mattress will void the product’s warranty. But if you’re past the warranty period, you may go ahead and cut your memory foam mattress.
  • Check the label of the mattress if it contains fibreglass. Fibreglass is used on low-cost mattresses as a fire retardant. When cut and exposed to air, fibreglass particles can irritate the eyes, nose, and skin.  In this case, it would not be safe for you to cut the memory foam mattress.

If you’re decided to cut your memory foam mattress, and your mattress is safe for cutting, the best way to cut it is by using the right tools and techniques. You can start cutting by following our guide.

Step 1: Take off the mattress cover.

a woman and daughter in a bedroom
Image: Pexels

Depending on the manufacturer, your memory foam mattress might have zippers for opening the cover up or no zippers.

If there is no opening, use a pair of scissors to cut into the cloth.

If you are going to save the mattress cover for reuse, cut along the edges for easier restitching later.

Step 2: Measure and mark your cutting area

steel tape measuring a wood
Image: Pexels

Once you’ve determined the desired mattress size, measure that against your mattress and use a marker to outline where you need to cut.

Use a ruler or something like straight-edge cardboard as a guide.

Step 3: Cut the memory foam mattress

memory foam mattress with sheet unzipped
Image: Ikea

Place your mattress on a flat and stable surface. When you start cutting, make sure you’re not compressing the foam, as this will change the shape of the edge when cut.

Step 4: Trim the rough cuts

Sharp metal scissors
Image: Pexels

You won’t cut a perfect edge unless you use a machine. So it’s expected to have rough edges.

Trim these edges to make a straight edge. You can use scissors or an electrical knife for this method.

Step 5: Cover your new mattress

woman seated on mattress and vase of flowers
Image: Pexels

You can either

  • Reuse your old mattress cover by sewing the fabric using the new dimensions
  • Reuse your old mattress cover by fitting the fabric on the foam and using safety pins to secure the fabric
  • Open up Amazon to buy a new standard-sized mattress cover

And there you have it, you have your newly sized mattress!

FAQ: Can you cut memory foam with a hot wire?

Yes, you can use a hot wire to cut the mattress in half.

  • If you want to cut the mattress into two with the same thickness as the original, cut the mattress vertically.
  • If you’re going to make the mattress into a thinner mattress, cut the mattress horizontally.
Blue Steam Wire
Image: Amazon

If your case is the former, you can use the above steps. If your case is the latter, this is a lot trickier:

  • Have a companion that will assist you.
  • Lay the mattress on a flat and stable surface.
  • Mark the line horizontally on where you want to cut the mattress.
  • It is recommended to use an electric knife for this.
  • Start cutting horizontally along the short side of the mattress.
  • Ask your companion to lift the top part of the mattress that is being cut to cut through the middle.
  • Continue until the mattress is completely cut across.


Did you know? The UK threw away more than 7 million mattresses in 2017, which mostly went straight to landfills. So if your memory foam mattress is still in good condition, you are on the right choice of reusing or repurposing.

Besides, with the right tools, steady hands, and patience, you can easily resize your mattress to suit your needs. Ask a friend or partner for assistance for better results since memory foam mattresses are quite heavy.


  • Fiberglass. (n.d.). Retrieved from Washington State Department of Health:
Photo of author


Max Stevens

Chief Editor here at The Sleep Checklist. Suffered from a seemingly infinite knot in my thoracic area (between the spine and shoulder blade) due to my lifelong side sleeping habits. With my girlfriend, we look to provide the most relevant and best mattress advice.