Tattoo Session Planner

Total Hours is built from two multiplications, not one: Total Design Area is multiplied by a rate keyed to Design Complexity (0.1 hours per square inch for simple linework up to 0.4 for photorealistic, lines 14-18), and that result is multiplied again by a Color Work factor (1.0x black & gray, 1.2x some color, 1.4x full color, line 19). Pain Tolerance sets a hard ceiling on how long any single session can run, and that ceiling can override Max Session Length entirely: Low caps every session at 3 hours and Average caps at 5 hours regardless of what you typed for Max Session Length, while only High lets your own Max Session Length figure through unmodified (lines 23-24) -- so raising Max Session Length above 3 or 5 hours does nothing unless Pain Tolerance is set to High. Sessions Needed is a ceiling-rounded division of Total Hours by that effective session length (line 26), which makes it a step function: a small increase in Total Design Area near a whole multiple of your effective session length can add an entire extra session, not a fractional one.

Outline Time is capped at 30% of Total Hours or your effective session length, whichever is smaller (line 33), and Shading/Color Time is simply whatever's left over (line 34). Hours per Session is Total Hours divided by Sessions Needed -- an average across the whole plan, not the length of any specific session -- and because Sessions Needed jumps in whole steps, Hours per Session can actually go down right at the point where Total Design Area pushes Sessions Needed up by one, since the same (or slightly more) total time is now spread across an extra session.