- clearly define activities then break them down further until lowest-level activity estimates are two weeks or less
- clearly define activity start and end points
- involve the people who will perform the activity
- minimize the use of "fudge factors"
Duncan Haughey provides the following rules to help create accurate and realistic estimates. The website https://www.projectsmart.co.uk/estimating-project-costs.php also includes a list of common mistakes.
- Assume resources will only be productive for 80 percent of their time
- Resources working on multiple projects take longer to complete tasks because of time lost switching between tasks
- People tend to be optimistic and often underestimate how long tasks will take
- Make use of other people's experiences and your own
- Get an expert view
- Include management time in any estimate
- Always build in contingency for problem solving, meetings and other unexpected events
- Cost each task in the Work Breakdown Structure to arrive at a total, rather than costing the project as a whole
- Agree a tolerance with your customer for additional work that arises during the project
- Communicate any assumptions, exclusions or constraints you have to your customer
- Provide regular budget statements to your customer, copying your team, so they are always aware of the current position
Prior to creating my project schedule as a Gantt Chart, I created an Excel file for both my effort/duration table and my cost estimation worksheet. There are templates available that can be used in Excel for project planning, including this Project Cost Estimator, available at this site: http://analysistabs.com/excel-templates/project-cost-estimator-free-download/
This site also includes a number of project management templates for Excel, including Gantt charts, project budgeting and project timelines: https://www.smartsheet.com/top-project-management-excel-templates
I could not imagine performing these tasks (project scheduling, cost estimations, etc.) without the use of Excel and having pre-built templates would be very helpful for a beginner like myself.
Haughey, D. (n.d.) Estimating Project Costs. Retrieved from https://www.projectsmart.co.uk/estimating-project-costs.php
Portny, S. E. (2013) Project management for dummies, 4th edition. Hoboken, NJ: John Wiley & Sons, Inc.