Estimate your finish date in Onplana Schedule

A plan’s finish date is one number, and everyone knows it is a guess. Plan > Schedule risk… puts a chance on it. The app schedules the plan many times, each time with every open task taking a different length between its best and worst case, and counts how often the plan finishes by each date. It runs on your computer and writes nothing to the file.

Business and above

Run unlocks when the app is signed in to an organization on the Business, Enterprise or Enterprise+ plan. On any other plan the dialog opens and you can enter ranges and risks, but Run reads “Available with a Business workspace.” See Unlock the paid features of Onplana Schedule.

Run it

1. Give the tasks you know best a range. Open View > Columns and fields…, show the Optimistic and Pessimistic columns, and type each task’s best and worst case. Tasks without a range use the default range.

2. Choose Plan > Schedule risk….

3. Check the settings: Iterations (1,000 to start, from 100 to 5,000), Distribution (PERT or Triangular), the Default range for tasks with no estimate (Optimistic, percent shorter and Pessimistic, percent longer) and an optional Target date.

4. Add any Risks: something that may or may not happen. Give each a Chance (%), an Impact (work days) and the Tasks it delays.

5. Select Run. Stop ends a long run early.

Read the results

• P50 finish, P80 finish and P90 finish: half, four in five and nine in ten of the runs finish by these days.
• Chance of the plan date and Chance of the target.
• Chance of finishing by each date: the finish curve, with the plan and target dates marked. Show the curve as a table lists the same figures.
• Milestones: each open milestone’s planned date against its P80.
• How often each task was critical: the share of runs in which it was on the critical path.
• What moves the finish: how closely each task’s length tracks the finish. The highest are the estimates to get right.
• About this run: how many tasks varied, which were held still, the risks included, and the seed.

The ranges you type are saved in the file as the custom fields Duration1 and Duration3, named “Optimistic Duration” and “Pessimistic Duration”, so Microsoft Project keeps them. Risks are kept for the open plan only.

Example

A plant shutdown plan finishes on 30 June and the client asks how sure you are. You give the boiler inspection 4 to 12 days, add the risk “Spare parts arrive late” with a 30% chance, a 5-day impact and the reassembly task, and select Run with 1,000 iterations. The P80 finish is 9 July and the Chance of the plan date is 22%. What moves the finish puts the boiler inspection first, so that is where you tighten the estimate or add a crew.

Limits

• Each task’s length is drawn on its own. On real projects delays travel together, so the true spread is usually wider and these dates lean optimistic. The dialog says so beside the results.
• Summary tasks are left out; their subtasks vary.
• A plan with a dependency loop cannot be scheduled, so it cannot be run.
• Risks are not saved in the file, because Project XML has no place for a risk register.
• The run has no history on the desktop. To keep runs and share them, use Schedule Risk on a project in Onplana: see Estimate how likely your finish date is.

FAQs

Does a run change my plan? No. It schedules copies of the plan. Only the ranges you type are saved, on their tasks.

Why is the chance of the plan date low? The plan date assumes every task takes exactly its planned length. In a run, some tasks run long and where two paths meet the later one sets the date, so finishes tend to land after the plan.

Why do two runs differ a little? Each run draws new lengths. More iterations bring them closer together.

Why does it need Business when the other paid commands need Pro? Schedule risk analysis is a Business feature in Onplana on the web, and the app follows the same plans.