How to Make a Cooler out of a Cardboard Box

How to Make a Cooler out of a Cardboard Box

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Keep perishables cool on your next car camping trip by constructing your own cardboard cooler. DIY coolers may not be quite as effective as their commercial counterparts, but their low cost helps to offset this small difference in quality. Additionally, you can make one in any size you like, and tailor it to fit your car perfectly.

Items you will need

  • Cardboard box

  • Knife or razor blade

  • Tape measure or ruler

  • Water sealant

  • One-inch-thick foam sheets

  • Silicone adhesive

  • Pencil or screwdriver

  • Thumbtacks

  • Rubber band

Step 1

Remove and discard the two small flaps from the cardboard’s opening with your knife. Cut one of the larger flaps off and set it aside. Leave the single remaining flap in place.

Step 2

Spray the entire box -- inside and outside -- with the water sealant. Allow the box to dry for at least 24 hours, and then apply a second coat. Allow the box to dry an additional 24 hours.

Step 3

Turn the box so that the opening faces the ceiling. Measure the internal dimensions of the bottom of the box with the tape measure. Use the knife to cut a piece of foam to the same size. Place the foam on the bottom of the box, and ensure it fits snuggly against the sides.

Step 4

Measure the internal dimensions of the two narrow sides of the box. If your box is square, simply pick two facing sides. Use the knife to cut two like-sized pieces of foam. Place the foam in the box, against the walls and ensure a good fit.

Step 5

Measure the internal dimensions of the two remaining walls. Cut foam pieces of equal size using the knife, and place the foam panels in the box. The box should now have a foam floor and four foam-covered sides. Once you are sure the foam panels are properly sized, you can use silicone to hold them into place, but it is not necessary if the foam panels fit together tightly. Be sure to allow the silicone to dry before proceeding.

Step 6

Cut the final piece of foam with the knife to make the top. Make it the same size as the piece that covered the floor. Then remove an additional inch of material from each side to allow the final piece to fit inside the four foam panels covering the walls.

Step 7

Squirt a bead of silicone on one side of the top foam. Press the foam against the only remaining cardboard flap – the cardboard flap should cover half of the foam. Take the long flap that was removed earlier and press it to the foam so that it lines up with the flap still connected to the box. You should now have a one-piece top, which opens on one side, rather than in the middle. Allow the silicone to dry completely before use.

Step 8

Punch a single hole in the bottom of one of the cooler’s walls with the pencil – penetrate the cardboard and the foam. This forms a drain, which allows you to pour out water as the ice in your cooler melts.

Step 9

Insert one thumbtack in the lid of the box, and stick another thumbtack on the side of the box. Stretch the rubber band between the two thumbtacks to keep the lid shut.


  • If you do not intend to use the cardboard box multiple times, you can forgo the water sealant.
  • You can purchase foam sheets at big box department stores, but they are often less expensive when purchased at hardware stores or craft shops. Additionally, it is often more economical to purchase a large sheet and cut it down yourself, rather than buying multiple small sheets.
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