Dot grid paper, ¼ inch, for A4

Dots are the right paper for drawing shapes, arrays and number lines: there is something to measure against, but nothing crossing what has been drawn.

It is also the usual paper for bullet journals and hand-drawn plans, which is why a page of it is worth having in the printer tray whatever age is using it.

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 A4 — 210 × 297 mm. 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 US Letter.