How to Make a Periscope from Cardboard

Learn to build a working cardboard periscope with your kids using simple household materials and mirrors.

  1. Gather Your Materials. You'll need a long, narrow cardboard box (like a wrapping paper tube box or cereal box), two small mirrors (about 2-3 inches wide), tape, scissors or a craft knife, a ruler, and a pencil. If you don't have mirrors, you can use reflective materials like mirror tiles from a craft store or even old CDs as a substitute, though mirrors work best.
  2. Prepare the Cardboard Tube. If using a flat box, tape it into a rectangular tube shape. The tube should be at least 12 inches long and wide enough for the mirrors to fit at an angle. Clean out any debris and make sure the inside is as smooth as possible for the best reflection.
  3. Mark the Mirror Positions. Measure about 2 inches from each end of the tube. At these spots, you'll cut viewing holes and mirror slots. The key is positioning the mirrors at exactly 45-degree angles to reflect light properly up through the tube.
  4. Cut the Viewing Holes. Cut a rectangular hole about 1 inch by 2 inches on one side of the tube, near one end. This is your viewing window. At the opposite end, cut another hole of the same size on the opposite side of the tube. Adults should handle the cutting for younger children.
  5. Create Mirror Slots. Cut diagonal slots inside the tube to hold your mirrors at 45-degree angles. The slot near the bottom viewing hole should angle the mirror to reflect light coming through the hole up the tube. The slot near the top should angle the mirror to reflect that light out through the top viewing hole.
  6. Install the Mirrors. Carefully slide the mirrors into the slots, making sure the reflective surfaces face the correct directions. The bottom mirror should face up and toward the top of the tube. The top mirror should face down and toward the viewing hole. Secure with tape, being careful not to cover the reflective surfaces.
  7. Test Your Periscope. Hold the periscope upright and look through the bottom viewing hole while pointing the top toward something you want to see. You should see the reflection of whatever is in front of the top of the periscope. If the image is unclear, adjust the mirror angles slightly.