Where the shape comes from
A long-handled ladle, drawn as a bowl on a stick and shown tipped to pour — the same shape that measured out roughly ten litres of grain and gave its name to the unit, and that traced the ladle-shaped Big Dipper, 北斗, across the night sky. Grain measured out by it gives 料, material, to gauge; grain divided by it into categories gives 科, a branch of study, a department.
汉字 filed under 斗
No published character on HSK Guide is filed under this radical yet. 汉字库.