How To Cut A Memory Foam Mattress Topper?

by Max Stevens

The time has come to finally learn how to cut a memory foam mattress topper. Whether you need to cut your topper to resize it, or you want to repurpose the foam for another use – this guide is the A-Z you need.

Suppose you don’t know how to properly cut memory foam. In that case, you risk the possibility of cutting the wrong size and damaging the memory foam. Not the optimal outcome when you need to use it.

If you damage your memory foam mattress topper to the point where it can’t be repaired, it’s worse as you need to buy a new one to make your bed comfortable. Your money, efforts, and time are all wasted in a single mistake.

To avoid those kinds of situations, it’s good to know what you’re doing. So let’s crack on!

Tools & Materials Needed

Before we go to the actual steps, make sure to gather these tools and materials first so everything will be up and ready as you go through the steps:

  • Long ruler (or tape measure)
  • Sharpie or any other marker
  • A very sharp knife
  • Electric knife (recommended)
  • Big scissors

Cutting a Memory Foam Mattress Topper Step-By-Step

Here are the steps to follow:

Before you do anything we’ve listed below, let us remind you first: cutting your memory foam mattress topper will VOID its warranty. So only do this if your mattress topper has outlived its warranty period.

Step 1: Take Off the Mattress Topper Cover

The first step is to remove your memory foam mattress topper cover since you don’t want to puncture or cut it (you can still use it later).

If the mattress topper cover has zippers, just pull the zipper to open it up and pull the memory foam to separate it from the cover. However, if the mattress topper has no zippers or any other way to open it, you have no choice but to cut it up.

Using big scissors, gently pull the cover away from the foam inside (leaving at least an inch of space between the cover and the foam). Once the cover is pryed away, cut the cover open just enough to take out the foam.

Remember to do this gently to prevent damaging the memory foam.

Step 2: Lay the Topper On a Flat Surface

Find a clean and dry flat surface where you can lay the memory foam mattress topper. Make sure the area is unobstructed so you can work freely and without damaging anything around.

If you’re wondering, laying the topper on a flat surface is needed since you can’t mark out the lines you want to cut if the mattress topper is standing vertically; it’s very difficult to do so.

Step 3: Mark the Lines You Want to Cut

After laying your mattress topper flat, grab your Sharpie or similar marker and your measuring device (either a ruler or a tape measure).

Mark out the lines you want to cut and carefully do it, so the lines remain precise. You may mark out lines that fit different sizes of mattress topper you have in mind but do this carefully, so your topper remains intact.

Step 4: Cut the Memory Foam Without Putting Pressure On the Foam

Grab your sharp knife or your electric knife (recommended), and cut the foam without applying pressure or compression.

Applying pressure while cutting shifts and changes the blade’s angle, which will mess up the measurements you’ve marked earlier. Imagine marking out perfect lines on step 3 to mess up the cutting part on step 4. That’s not a good thing, isn’t it?

To avoid putting pressure while cutting, ensure you have a very sharp knife or use an electric knife to make things easier.

Step 5: Finishing Touches

Once you’ve successfully cut the memory foam mattress topper, carefully check every side and corner of the mattress topper.

Once you see some sides that do not fit into the measurements you’ve made earlier, trim them off accordingly using your knife or electric knife.

What Is The Best Way To Cut Memory Foam Mattress Topper?

The best way to cut a memory foam mattress topper is to use power tools such as an electric knife, or electric hand saw so you can cut precisely and quickly.

Using a knife manually is tiring and not precise since the human hand cannot and will never be able to maintain a perfect cutting angle at all times.

You can also use the hot-wire method though it would also take longer (just a little bit quicker than using a handheld kitchen knife), and it’s also imprecise. Let’s elaborate down below.

Hot Wire Method

The hot wire method is pretty simple and straightforward: you heat a metal wire and use it to melt and cut the memory foam mattress topper.

To do this, first, buy metal wire from your local hardware store and buy some candles. If you’ve bought a roll of metal wire, cut a 6-7 inches long wire using a wire cutter.

Light up a candle using a lighter or a matchstick, use some gloves (you don’t want to get your fingers burned), and then put the metal wire directly on the fire.

Wait for around a minute and cut through the memory foam using the hot metal wire. Reheat the metal wire repeatedly until you’ve completed cutting the mattress topper.

In case you’re wondering, candles can burn up to 1400 degrees celsius, enough to heat the metal wire to the point where cutting the memory foam is a literal piece of cake. It can mess up the foam and your measurements if you have shaky hands.

Can You Cut a Memory Foam Mattress Topper With Scissors?

It depends on the memory foam mattress topper thickness and density. If the mattress topper is only 1-2 inches thick, you can definitely use large scissors to cut it.

With just the thickness of the mattress topper in play, suppose your topper is 3-4 inches thick, your scissor would have a hard time cutting the material, and you may need to apply pressure while cutting, which is not advisable since the cutting would be imprecise once you apply pressure.

With both mattress topper density and thickness in play, a thick and dense topper would resist cutting from big scissors. You’ll need a powerful electric handheld saw to cut it out.

To understand typical mattress topper density ranges, we’ve outlined them below:

  • A memory foam density below 3.5 lbs is low-density.
  • A memory foam density between 3.5 to 5.0 lbs is medium density.
  • A memory foam density topping over 5.0 lbs is high density.

These density ranges can vary by manufacturer, so check your mattress topper’s tags and/or labels and look for their density ranges to be sure.

Is It Safe To Cut a Memory Foam Mattress Topper?

It depends on what sort of “safe” you’re talking about. If you’re talking about if the product’s warranty is safe when cutting, it’s a big no-no. Your mattress topper warranty will be voided.

If you’re talking about your physical safety when cutting, yes, it is safe. Ensure you work in a controlled environment where you won’t cut yourself accidentally.

If you’re going for the hot wire method, you may inhale the fumes of melted memory foam, so it can pose a respiratory risk.

Memory foam mattress toppers are also bound to regulations of being fire-resistant. With this in mind, manufacturers have added fire retardant chemicals to memory foam to help prevent it from catching fire quickly.

One renowned dangerous fire-retardant chemical is polybrominated diphenyl ethers. However, this has since been banned by US authorities and the European Union.

If using the hot wire method, please ensure you use a respirator mask to be safe from inhaling chemical fumes once you cut the foam using a heated metal wire.

How Do You Cut 3-4 Inches Thick Memory Foam Mattress Topper?

Using a manual knife to cut a 3-4 inches thick memory foam mattress topper would take decades. And we’re not even talking about mattress topper density.

So instead of manually cutting the topper, you should use an electric knife or saw. These power tools do all the hard work for you, and all you need to have is steady hands and precise measurements.

You can also go to an upholstery shop and let them do the measurements and cutting, so the results would be good (since they’re professionals).

How to Cut a Memory Foam Mattress Topper Horizontally?

Cutting a memory foam mattress topper horizontally is no different from the steps we’ve taught you above. The only difference is it takes longer since you’re cutting horizontally.

We suggest using power tools to ease and speed the cutting process. And you could also go to your local upholstery shop and let the professionals cut your memory foam mattress topper perfectly. You’ll get a cut memory foam mattress topper without breaking a sweat.

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.