none
Modification of the Work/Units/Duration formula used by Project RRS feed

  • Question

  • I have several years' experience of using Microsoft Project, predominantly to plan and track projects using the gantt chart functionality.  I have tried using the resourcing component of Project on several occasions in the past with much frustration, as I have not been able to get Project to do what I want.

    I understand that the three variables used by Project are Work (in my case, hourly inputs of resources); Duration (the length of tasks); and, Units (which I understand to be the 'peak %' utilisation of resources).  I also know that Project allows the user to fix whichever variable they choose and then automatically updates the others variables when there are changes to the inputs.  For example:

    - If Work is 'fixed' and changes are made to Duration, Project automatically recalculates Units (reflected in the resource usage sheet).

    - If Duration is 'fixed' and changes are made to the number of Works hours, Project automatically recalculates the Units.

    The problem for me comes when, for example, I am preparing a proposal and the timescales (and therefore duration of tasks) are fixed in order to meet key milestone dates prescribed by the Client, and the budget is also fixed, based on our best estimate of the amount of Work required to complete each task.  In this scenario, I would like to be able to fix Duration and Work and for Project to only recalculate Units.  Being able to effect this change would make Project so much more useful for me during the preparation of proposals and for subsequently tracking earned value during project delivery.

    Is there a way to modify these relationships? I wonder if this is only possible by editing the code behind Project?  On the face of it, the change to the coding would be relatively straightforward - just switch the references to Work/Units/Duration in the relevant formulae.  Does anyone know if this is possible?

    Thanks in advance


    Monday, April 13, 2015 2:17 PM

Answers

  • And you dont even have to change 'all' tasks. you can edit the task type of just that task, make your change and then change it back if you like.

    There should also be an option that pops up as a 'smart tag' if you edit the duration or work in a Gantt view that will give you the option to change how the formula gets applied.

    In this example I have a Fixed Units task that had a duration of 1 day. I changed the duration to 4 days. It put a little green 'tab' in the upper left corner of the Duration field. I hovered over the field and the yellow sign with the exclamation sign popped up. Click on that and you get the option to "increase work but keep Units the same" or "Decrease the hours resources work per day but keep the same work."

    So that might help as well.


    Brian Kennemer - Project MVP Principal Architect Projectified Consulting http://www.projectified.com

    Tuesday, April 14, 2015 4:27 PM
    Moderator

All replies

  • Hi,

    You are here in a mathematical paradox. You have a equation with 3 variables. You cannot fix 2 of them and change only 1. Except if you go into other ensemble of numbers, you cannot do that, so neither Project does, even with some coding solution.

    If you do need to change the units, this means that the resources will work more or less than planned. Thus either we'll do more/less work or the tasks will last longer/shorter. Otherwise this is your scope that is not the same anymore.


    Hope this helps,


    Guillaume Rouyre, MBA, MVP, P-Seller |

    Monday, April 13, 2015 2:35 PM
    Moderator
  • Stubberfield,

    Maybe it's too early and my brain isn't fully functional yet but I'm lost as to why a fixed duration, non-effort driven set of tasks won't do what you need. Project's basic work equation is:

    Units = Work/Duration

    If the duration is a given and the work is also a given, then units will be calculated. I thought that is what you wanted.

    Since the timeline is driven by key milestones it is a fixed time. Work is based on best estimates so it's not quite fixed, but given the first best estimate value, Project will calculate the assignment level of resources necessary to do any given task. If the work is re-estimated, (e.g. better information becomes available), adjusting the work value will re-calculate the assignment level. Isn't that what you are trying to do?

    Note, Project has been used for years for doing proposals. Normally a customer may dictate a timeline and a budget but those are really goals to be met. Given the scope of a project, a ground-up estimate will produce a plan that may or may not meet the timeline and/or budget. If the plan dovetails with the customer's needs/desires, then great, but if not, a negotiation of requirements (e.g. larger budget, longer timeline, less scope) is in order.

    John

    Monday, April 13, 2015 3:10 PM
  • Hi Guillaume and John 

    Thanks for the replies.  In an attempt to clarify my earlier post, what I really want to do is to:

    1. Create a Gantt Chart in the normal way, adding tasks, setting linkages between tasks and prescribing the duration of tasks.

    2. Define resources in the resource sheet and assign them to the relevant tasks.

    3. In the resource usage sheet, allocate work hours per resource per task.

    4. Following initial set-up of the project, I would then like to have the flexibility to either:

    a) modify task duration without affecting the amount of work; or

    b) modify amount of work without affecting the duration of tasks.

    *****************************

    In the midst of writing this reply, I have realised my mistake:

    I had originally thought I could only assign a task as either 'fixed duration' or 'fixed work' and then be stuck with that choice thereafter and not have the flexibility to change task type later.  Whereas all I need to do is:

    - If changing the duration of a task and not wanting to update the amount of work, change the 'type' of all tasks to 'fixed work'.

    OR

    - If changing the amount of work and not wanting to update the duration of tasks, change the type of all tasks to 'fixed duration'.

    Thanks for helping me get there...

    Cheers


    <o:p></o:p>

    Tuesday, April 14, 2015 4:14 PM
  • And you dont even have to change 'all' tasks. you can edit the task type of just that task, make your change and then change it back if you like.

    There should also be an option that pops up as a 'smart tag' if you edit the duration or work in a Gantt view that will give you the option to change how the formula gets applied.

    In this example I have a Fixed Units task that had a duration of 1 day. I changed the duration to 4 days. It put a little green 'tab' in the upper left corner of the Duration field. I hovered over the field and the yellow sign with the exclamation sign popped up. Click on that and you get the option to "increase work but keep Units the same" or "Decrease the hours resources work per day but keep the same work."

    So that might help as well.


    Brian Kennemer - Project MVP Principal Architect Projectified Consulting http://www.projectified.com

    Tuesday, April 14, 2015 4:27 PM
    Moderator
  • Hi Brian

    I hadn't seen the smart-tag option before.  That works just as well as changing the task type. 

    Thanks 

    Wednesday, April 15, 2015 11:40 AM
  • In addition to Brian's excellent advice and your reply, I'd mention that the smart-tag action will not change the task type. It just a way Project uses to ask you arbitrating a conflict between the previous action and the task type.

    Hope this helps,


    Guillaume Rouyre, MBA, MVP, P-Seller |

    Wednesday, April 15, 2015 12:15 PM
    Moderator