Things You'll Need
Ruler or yardstick
Scissors or electric knife
If you are using an electric knife, don't force it or you will get a jagged edge.
Do not try to cut memory foam that is more than 2 1/2 inches thick with scissors. If you are using an electric knife, follow all safety instructions.
A good night's sleep is crucial in this busy world. A memory foam topper is a great way to revitalize an older mattress, or soften a too-hard new one. Whether you make your own mattress topper or buy a pre-made one, you may have to trim it to fit. Most manufacturers make the foam topper a little larger than the actual mattress, which can make it difficult to use with your fitted sheets. Fortunately, trimming a memory foam topper is easy.
Decide what size mattress topper you need. Mattresses come in standard sizes, so if you don't know what size your mattress is, you can measure it. Few manufacturers still make full-sized beds, so if you have an older mattress, you will need to measure it. Here are the standard sizes: Twin: 39 inches by 75 inches (99 by 191 cm) Long Twin: 39 inches by 80 inches (99 by 203 cm) Full: 54 inches by 75 inches (137 by 191 cm) Queen: 60 inches by 80 inches (152 by 203 cm) King: 78 inches by 80 inches (198 x 203 cm) California King: 72 inches by 84 inches (183 by 214 cm)
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Lay the memory foam out on a raised, flat surface, like your kitchen or dining room table. Make sure the edge you are cutting hangs over your table edge, so that you don't damage your table.
Use a permanent marker and a ruler or yardstick to mark the line you need to cut.
Use the electric knife or scissors to cut along the line you have drawn. Stop often to make sure that the foam is straight and that you are following the line correctly.