How to Make a Cardboard Megaphone – Easy Cardboard Megaphone DIY Project

Learn how to make a megaphone from cardboard with simple tools. This step-by-step DIY cardboard megaphone tutorial includes dimensions and is perfect for crafts, school projects, or events.

Step-by-Step Instructions: How to Make a Cardboard Megaphone

A simple cardboard megaphone can be made from a single sheet of light cardboard by cutting a curved pattern and rolling it into a cone.

How to Make a Cardboard Megaphone

Materials

  • Light cardboard
  • Pin or thumbtack
  • Strong thread
  • Pencil
  • Ruler
  • Scissors or craft knife
  • Brass fasteners (split pins), staples, or tape

Choose a Size

Full-Size Megaphone

  • Cardboard sheet: 30 in × 30 in (76 × 76 cm)
  • Inner radius: 5 in (12.7 cm)
  • Outer radius: 29 in (73.7 cm)

Finished size (approx.):

  • Length: 28–29 in (71–74 cm)
  • Bell diameter: 18–19 in (46–48 cm)

Half-Size Megaphone

Simply divide all dimensions by two:

  • Cardboard sheet: 15 in × 15 in (38 × 38 cm)
  • Inner radius: 2½ in (6.4 cm)
  • Outer radius: 14½ in (36.8 cm)

Finished size (approx.):

  • Length: 14–15 in (36–38 cm)
  • Bell diameter: 9–10 in (23–25 cm)

Step 1 – Mark the Center

  1. Place the cardboard on a flat surface.
  2. Find the center of one edge.
  3. Push a pin through the cardboard at that point.

Step 2 – Make a Drawing Compass

  1. Tie a loop of thread around the pin.
  2. Tie two knots in the thread:

Full-Size Version

  • First knot: 5 in (12.7 cm) from the pin
  • Second knot: 29 in (73.7 cm) from the pin

Half-Size Version

  • First knot: 2½ in (6.4 cm) from the pin
  • Second knot: 14½ in (36.8 cm) from the pin

Step 3 – Draw the Arcs

Using the pin as the center:

  1. Draw a small arc using the inner knot.
  2. Draw a large arc using the outer knot.

The small arc forms the narrow end of the megaphone and the large arc forms the bell.

Step 4 – Draw the Side Lines

Right Side

Draw a straight line from the pin to the point where the large arc meets the right edge.

Left Side

Draw a straight line from a point:

  • 1 in (2.5 cm) left of the pin on the full-size version
  • ½ in (1.3 cm) left of the pin on the half-size version

to the left end of the large arc.

Overlap Line

Draw a dotted line from the pin to a point:

  • 1½ in (3.8 cm) from the left end of the large arc on the full-size version
  • ¾ in (1.9 cm) from the left end on the half-size version

Do not cut this dotted line.

Step 5 – Cut Out the Pattern

Cut along:

✅ The small arc
✅ The large arc
✅ Both solid side lines

Leave the dotted line untouched.

You should now have a curved sector-shaped piece similar to the original layout drawing.

Step 6 – Form the Cone

  1. Roll the cardboard into a cone.
  2. Bring the right edge over the left edge.
  3. Continue until the right edge aligns with the dotted line.

Adjust until the cone is round and symmetrical.

Step 7 – Fasten the Seam

Secure the overlap using:

  • Brass fasteners (traditional method)
  • Staples
  • Strong tape

Place fasteners evenly along the seam.

Step 8 – Reinforce the Openings (Optional)

For extra durability:

Full-Size Version

  • Cut a strip 1 in × 24 in (2.5 × 61 cm)

Half-Size Version

  • Cut a strip ½ in × 12 in (1.3 × 30 cm)

Wrap the strip around the large opening and secure it with glue or tape.

You may also fold the narrow end outward slightly to create a stronger rim.

Using the Megaphone

Hold the small opening close to your mouth and speak directly into it. Aim the large opening toward your audience for maximum sound projection.

Tips

  • Use lightweight but stiff cardboard.
  • Keep the cone as round as possible.
  • Seal gaps in the seam with tape.
  • A smooth cone projects sound better than a dented one.
  • Decorating or painting the outside will not affect performance.

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