How to estimate project time and resources

Accurate time estimation is a crucial skill in project management. Without it, you won’t know how long your project will take, and you won’t be able to get commitment from the people who need to sign it off.

Even more importantly for your career, sponsors often judge whether a project has succeeded or failed depending on whether it has been delivered on time and on budget. To have a chance of being successful as a project manager, you need to be able to negotiate sensible budgets and achievable deadlines.

Accurate time estimation is a skill essential for good project management. It is important to get time estimates right for two main reasons:

  1. Time estimates drive the setting of deadlines for delivery and planning of projects, and hence will impact on other peoples assessment of your reliability and competence as a project manager.
  2. Time estimates often determine the pricing of contracts and hence the profitability of the contract/project in commercial terms.

Generally you would perform tasks estimates from the bottom up, meaning each task is given an estimate which is then rolled up into the overall project estimate.  Naturally, this is called Bottom Up Estimating.  Within each task then, you can employ one of three estimating techniques:

  1. Analogous Estimating.  This is when you make an analogy to the same, or similar, task that has been performed before.  This is the best source of information because actual work completed, even if it requies adjustments, is extremely reliable.  For example, if your project is for building a driveway and you’ve done it before, you clearly have a head start.  Oftenyou have to make some adjustments, but the starting point is tremendously valuable.
  2. Parametric Estimating.  In this method the work is drilled down into a unit cost, for which an estimate exists from published data or prior experience.  For example, the cost per square foot of log home can be gleaned from previous projects.  In the engineering industry almost everything is done this way, from the engineering time down to the construction materials.
  3. Three point estimating.  If you’re not sure but can readily put an upper and lower bound on the value, this method is for you.  With a three point estimate you choose an optimistic (a) and pessimistic (b) estimate in addition to the normal, most likely (m) one.  Then a distribution can be chosen to arrive at the final estimate.
    1. Normal distribution:  te = (a + m + b) / 3.
    2. Beta distribution:  te = (a + 4m + b) / 6.

Talk to the Experts

You can do much estimating on your own, and even seek historic data to place your project in a larger context, but time estimating should not be done in isolation. Speaking to a person who has worked on similar projects will uncover nuance and details not found in dry data.

Experts are great, but there might be people close by, untapped. We’re speaking about your colleagues. Teams are assembled for expertise and experience. Talk to us, listen to their ideas and concerns.

Chances are team members have done similar projects and have resolved issues that might have sidetracked them in the past. They can give you thoughts about efficient and effective planning, including a better sense of how long everything will take.

Project planning and critical roadmap

The project program must be approved and signed by the stakeholders and functional managers.

This ensures that everyone is familiar with the program, including dates and resource commitments.

In addition, (written) confirmation will be required that resources will be available as indicated in the planning.

Once approved, the program will become the baseline for the rest of the project.

The progress of the project and the completion of activities will be monitored compared to project planning to determine if the project is running as planned.

A delay in any of the activities in the critical roadmap will delay the entire project.