Estimate effort as ranges, not single numbers

Someone wants a date and you only honestly have a spread.

Estimate the work below. Give ranges, never single numbers.

For each item:
1. Best case, likely, and worst case, with the reasoning behind the worst case specifically.
2. What drives the spread: unknowns, dependencies, review cycles, environments, or a person who may not be available.
3. A confidence rating, and what would raise it. If the answer is "a day of investigation", say so, that is often the right next step.

Then:
4. Give a total with the ranges combined honestly, not by adding the likely cases.
5. List the work that is usually forgotten in estimates like this: migration, backfill, analytics, error states, documentation, rollout, support handover.
6. Name the single item most likely to blow the estimate.

Work to estimate:

Prioritising and scope. Deciding what makes the cut and what the plan actually is: backlogs, MVPs, estimates, roadmaps.