Scheduling Blog Series Part 4: Devil’s in the Duration

Schedule Blog Series Part 4: Devil’s in the Duration


A project schedule is constructed with activities.  Activities represent individual pieces of work, when organized properly, define how the project is to get completed.  Activities embody a name, duration, and optionally other data.  This article will discuss determining duration.

Type of Project Influences Duration Determination

How well you know the means and methods of executing your project determines how you should estimate activity durations.  Some projects have as their product a plan for an execution project. This requires managerial judgement to balance the quality and availability of resources to the challenges of the plan.  Judgement with simple math should determine durations.  This process is called Top-Down Estimating.  If sponsors expect the project to be completed in a time frame, allow an activity with 10-30% of the total duration for time reserve.   A good Top-Down estimating reference for many spheres of endeavor is the Pre-Project Planning manual by the Construction Industry Institute. 

An execution project produces something unique and tangible: a book, building, production facility, software, calculations, a rocket, control system, procedure, corporate charter, a drug.  Many of these projects use means and methods whose labor quantity is available from estimating libraries.  Labor quantity is used to determine duration.

Where the “Devil” Lies

Credit for “Devil in the Details” phrase goes to Adm. Hyman Rickover, the creator of the nuclear Navy.

Excessive Top-Down judgement in the execution schedule

These projects can have hundreds of activities in the schedule.  The “Devil” arises when durations derived solely from judgement are linked in series.  Errors in the durations multiply.  (I have seen this happen).   This practice will cast a bad light on a schedule.

Summary project administrative activities, however, can be individual activities lasting the duration of the project. 

Suggestions for duration estimation

A.     Include time for the resource to prepare for the activity

1.      The project manager, superintendent, or discipline leader authorizes the activity to begin.

2.      The assignee gets and studies official project documents, design and specifications.

3.      The assignee reviews means and methods with the Project Manager, superintendent, or discipline leader

4.      The assignee gets tools, software, and workplace ready for work


B.     Include time to make the finished activity useful for others

1.      Review the work for quality.  Did the activity meet the objective of its performance? 

2.      Anything learned that affects other parts of the schedule?

3.      Did the activity prove the project is going in the wrong direction?  Sometimes “going back is the quickest way on.” – C. S. Lewis

4.      As-builts and documentation

5.      Technical or management review of the results

6.      Report changes and modifications left to be done

7.      Notifying supervision that the activity is done


Calculating duration from estimating libraries

Activity Duration = Person-hours * 1 / (No. of Applied Resources) * Effort

A.      Using a spreadsheet or equivalent, break down summary tasks into individual activities.  List in rows in a column.

B.      Place the person-hours and team size from the library into columns aligned with the activity rows.  Adjust person-hours for degree of difficulty and the skill of the resources.  Designate a name responsible for the activity or a generic resource type (like “electrician”).

C.      The Effort term: consider the workplace and how efficient the resources will be.  Perfection is Effort = 1.  Reality is less than 1.  An example: If the general contractor prescribes all workers to attend a daily safety meeting, set a value between .9 and 1. 

Change Management Considerations

Calculating duration from estimating libraries is easy to prescribe, but is your organization set up for it?


A.      The head of operations should discuss using the estimating libraries for duration determination in a meeting with project managers and estimators.  Get their suggestions.  Assign an PM and estimator to develop a work specification.  Although this is straightforward, it gets others involved and helps secure buy-in.

B.      Try it on a few projects.  Have those involved present their experience with the project managers and estimators.

C.      Refine and implement the work specification.  Authorize it.

D.     Every several months, check how well actual experience agrees with the duration estimates. Improve the estimating library with the new knowledge.

E.      Make sure the official estimate is “locked down” and in a folder where people can access it.


Not much in the way of training is required here.  Most people have the capability to do simple formulas in a spreadsheet program.


A detailed project schedule requires a formality in estimating durations. Follow the proven steps in this article to improve the effectiveness of your schedules.


About the author:

Mark Ramsay, PE, PMP, is owner of Effective Project Solutions, LLC.  His past jobs included Project Engineer for DuPont Co., Global Project Manager for Millennium Chemicals, and Project Management Consultant for Johnson Controls, Inc.  Mark graduated from Princeton University with a Mechanical/Aerospace Engineering degree and earned a Masters in Technical Management from Johns Hopkins University.  He is certified in software quality by the ISTQB.  He has won numerous project awards throughout his career, successfully managing sophisticated projects up to $40 million.


About Effective Project Solutions (EPS):

Established in 2012, EPS develops and sells Program Leader task and scheduling software.  EPS also offers scheduling services to clients.  Program Leader is for those operating many small projects who want an alternative to “spreadsheet management” and a replacement for confusing large project software.  Please see for more information.