1 cm graph paper

One-centimetre squares are the default grid in most school maths departments outside the US, which is why exercise books and worksheets assume them. Because this sheet is generated as vector PDF rather than a scan, the 10 mm spacing is exact on paper — print at 100% (not "fit to page") and a ruler will agree with the grid.

Larger squares suit younger students, coordinate work and anything measured in centimetres. If you are plotting finer data or need more rows per page, drop to 5 mm; for imperial work use the quarter-inch sheet instead.