If you are planning to use a new piece of foam rubber to replace rotting foam from old cushions or perhaps for a new project like making seat cushions, you may not be able to find the exact right size of foam. If this is the case, you may have to custom shape the foam to your exact measurements. Foam rubber comes in many thicknesses and densities. These factors will determine what type of tool you will need to shape your foam rubber.
Choose to use scissors or a craft foam cutter if you are cutting craft-grade foam rubber. Most often, craft foam is used for pillows and seat cushions.
Make your measurements on the foam with a marker to the scale of what you will need for your seat cushion or pillow and start cutting outside the lines.
Never cut directly on the lines. It is smarter to have the cushion cut too big the first time so you can keep shaving more foam off to fit your slip cover. If you cut too much off the first time, it is almost impossible to add the foam back.
Select an electric table saw or hot knife for cutting and shaping thick density foam. Most often, craft cutters do not have a large enough blade to cut this industrial strength foam. This foam rubber may be used to create car seats or other industrial applications and comes in large slabs. The foam that is best for these applications require tools with larger blades.
Make generic marks from your measurements onto your foam pad before you start the cutting. Start with large generic shapes before making precise cuts.
Make your first cuts and hold the desired seat cover up to the foam. Mark the foam again with a market for a second round of cutting.
Continue to make more refined cuts, one cut at a time. Keep placing the seat cover on the form until the fit is right.
Always cut less than what you need. Better to make several cuts than one precise cut that is too small.
Always wear safety goggles when using a table saw.