Follow one fold at a time and pause whenever you want. Ask me about any step: why a corner lands exactly on a point, how the diagonal makes the triangle, or where the 45° angles hide.

Paper Samurai Helmet (Kabuto)

Fold a square into a helmet with two horns, and see the triangles and halves that build it

Start with a square, front side down. Fold it in half along the diagonal, corner to corner. The diagonal is a line of symmetry: the two halves are mirror images, and together they make a triangle with angles of 90°, 45° and 45°, with two equal sides. Turn the triangle so its long edge is on top.

Now fold each of the two 45° corners down to the bottom point. The fold line runs from the middle of the long edge to the middle of a short side. It is exactly the same distance from the corner and from the bottom point, so the corner lands right on the point. The paper becomes a smaller square standing on its corner. Its side is half of the first square's side, so its area is a quarter, and it is covered by 4 layers of paper (4 × ¼ = 1: no paper is lost).

Fold the two flaps up so their tips meet the top point. The fold line goes through the left and right corners, halfway down, and the tip lands exactly on top. Then fold each tip outward along a line that cuts its 45° angle into two angles of 22.5°. The two folded tips are the horns, and they are mirror images of each other.

At the bottom, fold the front layer up halfway, and then halfway again, to make the brim: each fold halves the strip. The last layer folds behind in one simple fold, and nothing is tucked into a pocket. Pause the animation at any step and ask the tutor why a corner lands exactly on a point, or how many layers the paper has.

Related Topics

Paper Garrison CapDart Paper AirplanePythagorean Theorem
How do you fold a paper samurai helmet?
Start with a square, front side down. Fold it in half on the diagonal and turn it so the long edge is on top. Fold the two side corners down to the bottom point, fold the two flaps up to the top point, and fold their tips outward as horns. At the bottom, fold the front layer up twice and fold the last layer behind.
What size of paper do I need to wear the helmet?
A square about 50 cm on a side, for example a newspaper sheet cut square, fits a child's head. A square cut from A4 or letter paper makes a small helmet for a toy or a doll.
Why does the corner land exactly on the bottom point?
The fold line is made of all the points that are the same distance from the corner and from the bottom point. In the isosceles right triangle that line goes from the middle of the long edge to the middle of a short side. Folding along it swaps the two points.
What is different from the paper soldier cap?
The soldier cap needs squash folds. The helmet uses only simple folds: no squash and no pockets. Both start from a square and both are mirror images, left and right.