Plan coloring sessions for relaxation.
Colouring is enjoyed in sittings, not in continuous hours, so the planning unit is the sitting rather than the total. Multiplying pages by minutes per page gives the work, dividing by your comfortable sitting length gives the number of sessions, and dividing that by sessions per week converts it into a calendar. Sessions are rounded up because a half-finished sitting still occupies an evening.
Total work
Total minutes = pages x minutes per page
Sessions and weeks
Sessions = ceiling(total minutes / sitting length); weeks = sessions / sittings per week
Simple patterns run fifteen to twenty-five minutes, while dense mandalas and detailed botanical pages commonly take an hour or more. Time one page of your usual book rather than guessing.
Not necessarily. The calming effect comes from sustained focus, which most people hold for twenty to sixty minutes before attention and hand comfort fade.