In P6 Professional, you can display total float on the Gantt Chart in both numerical and graphical forms. Let’s take a look.
The Gantt chart, at its core, is a visual representation of the project, listing tasks vertically and time intervals for these tasks horizontally. I always tell students that the Gantt chart is the heart and soul of scheduling software; therefore, the more you know about the Gantt chart and P6 Professional’s Gantt chart graphics features, the more accurately you can represent the true scheduling situation.
The two main graphical bars on the Gantt chart are critical remaining work bars and noncritical remaining work bars. Critical remaining work bars on the Gantt chart, colored red, are tasks that cannot be delayed without postponing the project’s end date. Noncritical remaining work bars have total float and are colored green. The total float associated with these work bars represents the number of days the task can be delayed without impacting the project end date by a proportionate amount.
Together, critical and non-critical work bars direct your attention to those work efforts that require your focus to keep the project progressing as planned. The red bar efforts, again, indicate tasks where no delay is acceptable. Whereas the green bars indicate efforts with leeway, and, perhaps, from which you can draw resources to your more pressing matters.
There can be a significant disparity in the total float among tasks. It is beneficial to display total float on the Gantt chart both numerically and graphically, providing project managers with robust insight into this measure of schedule leeway.
This article demonstrates the presentation of total float on the Gantt chart, both as arithmetic values and graphical bars, to further illuminate a schedule’s slack and latitude.
Demonstration
In Figure 1, we have our demonstration schedule.
Figure 1 illustrates several green bars on the Gantt chart. These are our tasks with total float: Install Conduit, Dig Cable Trench, Install Grounding, Install Bus and Jumpers, Install Fence, Lay Stoning, and Lay Roadway.
We can roughly gauge the magnitude of total float for each of these tasks by following the relationship lines from each task to its successor activities. But this is not precise. It would be helpful to have a numbered value to the right of each non-critical task bar, providing a definitive total float amount.
Numeric Total Float
To specify a numeric total float value for each non-critical task, we choose the bars button in the layout tool group, as shown in Figure 2.
In the Bars dialog box, Figure 3, we 1) select the remaining work bar, 2) choose the Bar Labels tab in the bottom details, and 3) click the + Add button in the lower-left corner of the Bar Labels tab.
This adds a label, Figure 4, at position ‘Right’, which is where we want to locate it.
Then, we select the ‘Total Float’ label from the Label drop-down menu and click OK, Figure 4. Our Gantt chart, featuring a numerical Total Float display, is presented in Figure 5.
In Figure 5, we have outlined in red to focus on the ‘Install Conduit’ and ‘Dig Cable Trench’ tasks. It appears that they have similar finish dates, but our numerical labels highlight the contrast between them: Install Conduit has a total float of two days, whereas Dig Cable Trench has a total float of thirteen days.
To investigate the reason for this disparity, we examine the successors of each task. From Figure 5, it is difficult to decipher each task’s successors. In Figure 6, we glean more insight by selecting the Install Conduit task and reviewing its successor relationship in the bottom details.
Its successor is the Erect Steel Structures task bar, colored red, which is shown to follow soon after the completion of the Install Conduit task. In Figure 7, we select the Dig Cable Trench task and inspect its successors in the bottom details.
It has three successors: Lay Control Cable, Lay Stoning, and Lay Roadway. From the Gantt chart, we observe that there are more than ten days from the conclusion of Dig Cable Trench to its successor, Lay Control Cable. Dig Cable Trench has two additional successors that appear to follow immediately afterwards. However, we find that each of these successors has significant total float, at 28 days and 26 days. This further investigation explains how Dig Cable Trench has significantly more total float than Install Conduit.
Because we labeled each non-critical task with a numerical total float value directly on the Gantt chart, we can readily see the total float difference between “Install Conduit” and “Dig Cable Trench”. And avoid having to tediously review each individual task’s successors in the bottom details. This demonstrates the utility of numerical total float labels on the Gantt chart.
Graphic Total Float
A visual bar for the total float duration would complement these precise numeric values, making it quicker to assess total float in the schedule. To do this, we click the Bars button in the Layout Tool group, as shown in Figure 8.
Then, in the Bars dialog box, Figure 9, we select the bar definition at the top of the list or stack of bar definitions and click the + Add button.
This creates a new bar definition, which we modify. First, we confirm that it is toggled to display, then give it a meaningful name: Total Float Bar, as shown in Figure 10.
In the next column, Timescale, we select Float Bar from the drop-down menu, as shown in Figure 10. We proceed in Figure 11 to (1) confirm that our Total Float Bar has been selected.
Then, in Figure 11, (2) click the ellipse to activate the filter. We toggle on the (3) ‘In Progress’ and (4) ‘Not Started’ filters, (5) choose the ‘Any selected filter’ matching criterion, and, finally, (6) click OK, Figure 11. The matching criterion in step (5) becomes important when one or more filters are toggled on. The ‘Any selected filter’ criterion is like joining the filters with the ‘Or’ conjunction. To capture it, the task must be either in progress or not started. This is an easier hurdle to leap over than the ‘All selected filters’ criterion, which requires both filters to be true for task capture.
Continuing, in the Bar Style bottom tab, Figure 12, for our Total Float Bar definition, we specify how the graphics display on the Gantt chart for our filtered tasks. We chose the medium thickness and low bar for our Total Float Bar graphics, as shown in Figure 12.
Figure 13 displays the full definition of the Total Float Bar.
Our resulting Gantt chart and Total Float Bar graphics are shown in Figure 14.
Great! We now have a visual representation of the total float for each uncompleted task with a total float greater than zero. But, if you had Sherlock Holmes’ ability for keen observation, you would notice something is not quite right with our tasks’ relationship lines on our demonstration Gantt chart, Figure 14. In particular, notice the relationship lines connecting tasks that have total float bars. Is there something amiss with them? Note that the relationship lines for these tasks connect to the Total Float Bars, rather than the current bars, which is not what we want. But why do they connect to the float bars in this way?
The answer to this mystery is that where your bar definition is in the bars dialogue box’s list or stack of bar definitions makes a difference. Relationship lines connect to those higher in the stack. Therefore, we must move our Total Float Bar definition down using the down arrow and place it below the Remaining Work and Critical Remaining Work bar definitions, as shown in Figure 15.
After implementing Shift Down and applying our Total Float Bar definition, our final Gantt chart, Figure 16, displays the Total Float Bars with their appropriate relationship line connections.
Much better! With only a cursory glance at Figure 16, we find that the Total Float Bars provide a quick visual representation of the total float duration for each task. And if we want precise values for detailed reporting, we can see from the position of each float bar to the right the numerical total float values.
Summary
On the Gantt chart, we can display total float numerically using the Bars dialogue box, specifically in the Bar Labels tab, which displays in the bottom details. The green bar indicates that you can safely delay the task with no negative impact on the project’s conclusion, while the numerical value specifies the exact maximum amount of acceptable delay. To visualize the total float durations, we created a Total Float Bar definition. The Total Float Bar provides a quick visual aid for efficiently assessing the total float of each task, and the arithmetic total float value provides an exact value for reporting.
The visual graphics and numeric values complement each other, allowing for the easy examination and reporting of tasks in the schedule that have total float, thereby accentuating their leeway and latitude.