Similar/same approach here.. I break the job down into individual tasks, estimate min + max for each of those, then multiply subtotals by (usually) 1.5 for "unk

Similar/same approach here.. I break the job down into individual tasks, estimate min + max for each of those, then multiply subtotals by (usually) 1.5 for "unknown unknowns". Initially the "max" total is almost always 3-4x the "min" total, which is a sign I need to go back and get requirements nailed down better. I ask questions and tweak numbers until "max" is <2x "min" and at that point I consider the estimate finished. Whoever needs the estimate can then make a decision based on those best and worst case scenarios. I do these numerous times a year for bits of work which are usually from a few weeks to a few months long, and they end up being accurate to the degree intended.