How does a pillow box close?

Glue only the side seam. Once dry, push both curved ends inwards and they spring into the pillow shape and hold each other shut.

What does the end curve depth change?

How deep the curved ends are, which sets how fat the finished pillow is. About a fifth of the width is a good starting point.

Thin card, around 250 to 300 gsm. Board that is too thick will not curve, and paper that is too thin will not hold the shape.

The curved-end pillow box. No glue at the ends at all — the curves lock into each other.

Type the size you need above, in millimetres, centimetres or inches.
Download the PDF and print it at 100% — never “fit to page”.
Cut every solid line and score every dashed line.
Glue the side seam, let it dry, then push both curved ends inwards. They will spring into the pillow shape.

How does a pillow box close?: Glue only the side seam. Once dry, push both curved ends inwards and they spring into the pillow shape and hold each other shut.
What does the end curve depth change?: How deep the curved ends are, which sets how fat the finished pillow is. About a fifth of the width is a good starting point.
What card works best?: Thin card, around 250 to 300 gsm. Board that is too thick will not curve, and paper that is too thin will not hold the shape.