Isometric graph paper, 1 cm

The larger triangle is the one to print for a first attempt at drawing a cube. Small isometric paper is unforgiving — a line drawn one row out is a corner that does not meet — and a child who has just been shown the trick needs the room before they need the detail.

The rows are spaced by the height of the triangle rather than by its side, here as on the quarter-inch sheet, which is what makes the grid genuinely thirty degrees rather than a squashed approximation of it. A centimeter triangle is therefore about 8.7 mm from one row to the next, and that number is the whole reason the drawing looks right.

The rules are drawn as real strokes at real sizes — not a picture of lines, and not a background tint. That matters more than it sounds: browsers drop background graphics when printing unless the reader has gone looking for the setting, so ruled paper made the obvious way looks perfect on screen and comes out of the printer blank. Put a ruler on this one. It is the size it says it is.

This sheet is set for US Letter — 8.5 × 11 inches. Paper size is not a preference here: sent to a printer loaded with something else, the browser shrinks the page to fit, and a ruling that has been shrunk is no longer the size it was chosen for. So there is a second copy of this sheet, ruled identically and measured for A4.