How to Cut Upholstery Foam (With Tools You Already Have)

Are you planning a project that uses upholstery foam? I just finished making an upholstered built-in bench for my kids’ bedroom and when faced with that giant slab of foam I paused for a second. While googling exactly how to tackle the project, I found a bunch of methods suggesting tools I didn’t have like electric carving knives (people still have those??).

In this back-to-basics post, I’m going to teach you how to cut upholstery foam, using a tool you already have.

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How to Cut Upholstery Foam

All you need to cut upholstery foam is a serrated knife, preferably on the larger side. And I bet you already have one — a simple bread knife is perfect for the job!

If you don’t already have one, this offset bread knife is perfect and only costs $11.

First, measure your foam and draw the cut lines

Grab a marker and a measuring tape and draw a guideline for your cut on the upholstery foam. It helps if you can find a large surface to work on, like your dining room table, but the floor works too.

Use the measuring tape to mark the length you need on the foam. Make dots at your desired length every few inches down the foam, then connect the dots using a straight edge.

Tip: Measure and cut the short edge first to get the length you need, and do the long side second. This way, you’re cutting the shortest possible length each time.

Then, you can cut the foam

Now you can actually cut the foam by following this set of guidelines:

  • Take your serrated knife and line it up with the cut line you drew.
  • Hold the knife blade parallel to the upholstery foam and make a deliberate, shallow cut along the entire line — in one direction only. If you saw back and forth, the foam will tear and/or cut unevenly.
Align knife to line on foam
  • Lift your knife, carefully place it into the groove and make your next shallow cut the same way you made the first.
  • Continue like this until you cut through to the other side.
  • Repeat along your second cut mark if you have one.

You’re done!

Cutting that upholstery foam was pretty easy, right? I hope this short post was helpful. Sometimes we just need a quick answer to our basic questions!

Bonus: If you’re looking for a good deal on upholstery foam, I get mine here. It’s under $25 for a huge slab, and the quality is great.