How to Cut Foam with 4 Easy Methods

Ever since people have been looking for ways to make their lives easier, foam cutters have been needed. However, something as simple as a sharp knife will not suffice, whether it is cutting up cushions or mattresses. This article provides you with some options on the different types of foam cutters for your needs and how to use them properly to get the best use out of your new tool.

How to Cut Foam Board Insulation? [5 Easy Steps]

Table of Contents

  • What is foam, and why does it need to be cut?
  • 4 Different Methods for Cutting Foam:
    • How to cut foam with a knife?
    • How to cut foam with scissors?
    • How to cut foam with an electric carving knife?
    • How to cut foam with a jigsaw?
  • What you can do with leftover scraps of foam
  • The benefits of cutting your foam instead of buying it pre-cut from the store
  • 10 Tips for cutting the right shape out of the foam
  • Safety precautions to follow when cutting foam

What is foam, and why does it need to be cut?

Foam is an excellent material that can be used for many different things. It comes in the form of light and thin insulation, which makes it perfect to use during craft time or when you want a low-budget option for home improvement projects. Foams are either made from polystyrene (for crafts) or polyurethane foam (mainly found at hardware stores), with some people preferring one over another depending on their needs- both have benefits! When cutting foam pieces out, make sure they’re cut according to what shape will best suit your project’s specifications because, without support, foams won’t hold their shape well enough by themselves.

Related: How to Build an Insulated Exterior Door? [Step by Step Guide]

4 Different Methods for Cutting Foam:

Cutting foam can be a tasking job, but did you know there are four different methods that work to make it easier? Read the below methods:

How to cut foam with a knife?

  1. Draw on the foam with a marker to create your desired shape
  2. Cut through the foam using a sharp knife, following along the drawn lines.
  3. Cut the entire length of one side, then flip over and do the same thing on the other side.
  4. Continue cutting until you reach an edge and then stop because it will be hard to measure accurately from there on out.
  5. If you need to measure for something in between, make your cuts perpendicular to each other or estimate as best as possible
  6. Use sandpaper or an emery board to smooth out any rough edges left behind.
  7. When all sides have been cut, take off any excess pieces by pulling them up with your fingers or using a razor blade if necessary.

How to cut foam with scissors?

  1. Lay the piece of foam out with the side you want to be cut facing down. This will help it maintain its shape.
  2. Make sure that your scissors are very sharp and that they slide over each other easily; otherwise, it might take a while to get through the thick material.
  3. Position both blades of your scissors near one end or corner of the white foam product, squeezing them together tightly and using short strokes (a method known as “sawing”). Take care not to rip any pull apart any corners in the process.
  4. Snip small sections at a time or make “v” cuts designed to produce smaller pieces for easier shaping. The best way is probably trial and error, which can take a while if you’re trying to cut a more complex shape.
  5. If you want thinner pieces, several swipes of the scissor blades over the same area might do the trick. This is another step that will require some practice and patience.

How to cut foam with an electric carving knife?

  1. Get an electric carving knife and place it firmly in your hand, with the motor on top and handle positioned towards you, and the blunt (i.e., non-cutting) side of the blade is facing away from you.
  2. Scoop enough foam to fit comfortably in your hand and hold it between your fingers, so there are at least three fingers exposed.
  3. Lay the blunt side of the knife directly above a part of foam that has not been previously cut through yet, with pressure being applied to the foam with your fingertips
  4. Cut through the foam while moving the blade in a circular or swirling motion (i.e., do not press straight down)
  5. Repeat until you’ve finished cutting the foam into a cool shape!

How to cut foam with a jigsaw?

  1. Tape foam to both opposites sides of the cut line that you just made using low-tack tape. This gives you something to hold on to when you need it.
  2. Switch on your jigsaw and connect a piece of metal to the cut line; this will create stability when you’re cutting the bulkhead, as well as giving an easy point for placing your fingers during rough cutting or detailed cuts.
  3. For rough cutting, use only pressure from one finger in front of where your saw is going and push forward with circular arm movements so that all parts are getting consistent contact with the foam (this allows smoother cuts by not having any bumps and making the material glide instead of potentially tear).
  4. For detailed cuts, use your entire finger on top and either push in or pull forward, depending on the angle you need to make.
  5. If your blade gets stuck or binds up, don’t force it; let go immediately so that you don’t wear out its teeth prematurely from unnecessary pressure. If this is a problem, file down some of the excess foam to catch some build-up onto the blade. (The more surface area touching the jigsaw at one point also means less wear.)
  6. When finished cutting, remember to clean all rough edges with sandpaper.

What you can do with leftover scraps of foam

There are many ways to use leftover scraps of foam. Try one of these projects for fun or tailor it to your own needs.

Styrofoam packing:

You can use the pieces for caulking gaps in styrofoam packing material and attaching it to crates/boxes when transporting fragile objects using improvised packaging solutions such as plastic wrap.

Insulation installation:

You could also fill any gaps or spaces with a few pieces of scrap Styrofoam insulation board on the interior walls and attic floors before tucking up installed batts/blowing. Gaps don’t usually have to be sealed separately, so this is an inexpensive way to fill them. If you have a more advanced project in mind, it might be possible to glue scrap insulation boards together and cut out custom shapes as necessary for the job.


For modeling/sculpting projects, one good way is to use foam scraps to make a mold that can be used to create plaster casts of your favorite objects or sculptures. When all the molds are set, break away and throw away the scraps or reuse them if necessary with other materials like clay, plaster, or even resin. With this method, you can get some exciting textures on objects without having to worry about reusing material from old garments since Styrofoam models will not release fiber dyes onto fabrics once dry. 

The benefits of cutting your foam instead of buying it pre-cut from the store

Cut your foam is not just good for your pocket; it’s also friendly to the environment. Of course, you have to buy a foam cutting knife and use electricity to power the machine at home, but these steps are necessary only once.

Along with providing numerous health benefits (i.e., less dust from unfinished pieces of foam), cutting your sheets eliminates all those pesky trips to the store – and that can make adding up how much money you’re saving from taking “the do-it-yourself method” a breeze!

You can also control size or shape more easily than when buying pre-cut varieties. It may sound like an intimidating task at first, but many people find that applying some creativity makes this process easier than going to the store.

10 Tips for cutting the right shape out of the foam

  1. Use a fresh, sharp blade so you’ll have low resistance when making cuts.
  2. Position yourself in the position to make carving easier. You can kneel on one knee with the foam on your other knee or use a sawhorse as an improvised table for this purpose if necessary.
  3. Make sure that both hands can hold onto the knife, which should be in their dominant hand or are equally comfortable with either hand (i.e., left-handed people may have trouble using their right hand to cut).
  4. Draw an “X” through the area of material you want to cut out of the top layer of sandwiching foam as close to where it starts underneath as possible and only
  5. Compare the shape of your item to your foam; take note of how big and small curves are, what their tangents look like, etc. Sometimes a lot of time is wasted by starting with the wrong area.
  6. Keep in mind that the nicer your shapes are on the outside, the easier it will be for people to see. The jawline is easy, so create excellent angles for a more appealing finish. You can also try a snowflake shape with two points.
  7. Always hold and draw the cutting tool perpendicular to the surface you are cutting to achieve accurate results with minimal mutilation of the shaped piece of foam.
  8. Take care to stay on the lines so your angles will be accurate. Don’t worry about pushing too hard with your blade- go slow and feel the edge through the foam. Use a professional scoring knife like our Precision Knife, which features an automatically self-sharpening high-quality, sharp blade.
  9. Cut only one piece of foam at a time; don’t let it stack upon itself or sit on top of one another as this can cause creases in your final shape and even trip you up if you’re not careful. Keep all pieces flat to help them maintain their integrity into near-flawless shapes for building.
  10. Know that it takes patience and practice! You will not get it perfect the first time – don’t worry!

Safety precautions to follow when cutting foam

Wear safety goggles to protect your eyes; if something explodes and you didn’t wear any protective gear like that, then you could be very seriously injured. In addition, eyes can swell shut or even rupture if there is enough blood flow in them to the point where they are no longer protected by a layer of skin when gas or some other material hits it at high speeds.

Keep children away from the space where the cutting happens, especially when your space is not too well ventilated. Children will either have their mouths open because they’re curious about what’s going on and why these loud noises are coming from within this sealed-up room, so they might ingest the foam pieces that fly out due to turbulence.

Final Words

What is the best way to cut foam? This question can be answered by looking at what you are making. Foam cutting machines allow for precision cuts and save time, but they do cost a little more than other methods. If your goal is to create very intricate pieces that require precise cuts, then this might be a good investment for you. However, if you want something less high-tech, try using an electric carving knife instead! While working with this method, you’ll need some patience as it takes longer and requires careful planning when drawing out your design, but once complete, it’s one of the easiest ways to get clean straight edges on any size piece of foam board or matting material.

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