One of the less discussed features in a good project managers arsenal is the ‘Critical Path’ of a Project. That’s probably because we don’t tend to spend too much time calculating the critical path by hand but rather we consult it as a part of the Gantt Chart in our Project Management Software. It doesn’t make it any less important though.
With the nice overhaul of our ProWorkflow Gantt Chart (including a Critical Path feature) coming up in a few weeks, we thought it would be an interesting exercise to look at the thinking path behind the concept.
If anything, it makes you appreciate technology a bit more.
First things first
To work out the critical path, you start the project as you always would.
The steps we mention feel a bit superfluous, but rest assured; they’re not. They are vital in getting the critical path right. What’s more, any painful errors in the critical path often boil down to taking short-cuts in these steps.
- Step 1: Break up the project into more manageable tasks.
- Step 2: Consider the dependencies. What tasks need to be completed before you can move on to the next one? Assess whether there are any tasks that can happen simultaneously. Really take the time to figure out how you can work this in the most efficient way. Rather than going for a simple waterfall (one task following on to the next) or parallel approach (all tasks happening at the same time), think beyond one or the other and aim for a smart mix of the two.
- Step 3: Because of the tight schedule you are on, you look at the time each task will take. Determine the start date and the end date of each task from an optimistic point of view, but also consider the same dates from a more pessimistic angle. In doing this, you take the dependencies in to account, as they will prevent the start from one task depending on the finishing of the previous one.
- Step 4: Since you are such a skilled project manager, you whip up a network diagram showing the progress of the project as well as the dependency chain between the different tasks. This is an important step, as it will avoid overlooking tasks and dependencies. Even when you use your project management software to show you the critical path, it’s a step you shouldn’t skip.
What is the critical path?
As you probably already know, the critical path tells you the longest time it will take to complete the entire project. This is important information because any delay on that path delays the entire project. In other words, the critical path tells you what the minimum time is you need to finish a project as well as which tasks have no wiggle room and which ones do.
In the real world, the critical path can also be a very valuable tool for when you become time strapped: you can shorten the entire project by shortening the critical path. For instance, you customer might need you to finish a project by a certain date. After you’ve worked your way through all the above steps, you realize that you’re a couple of days short to meet the customer’s request.
We’ll explain later on how you can do that. First let’s see what the importance is of a task without wiggle room to the projects finish date.
Total Float and Critical Tasks
Tasks are critical if they don’t have any room for delays. Any delay in that critical task activity also delays the finish date. The amount of wiggle room you have in a task is called slack or float in project management.
Total float (or float for short) is the time an activity can move earlier or later without affecting the project finish date.
This will give you a clear picture of a project’s timeframe and if it will meet its deadline. If it doesn’t you can make adjustments.
Total float is so important that it even has a formula:
Total float = late finish – early finish
There are guidelines on how to calculate the late finish and early finish called backward and forward pass, but we’ll leave those for another time. What is important to know is that if an activity’s total float is 0, it’s on the critical path. If an activity’s total float is more than 0, the activity can delay by that amount without affecting the finish date. These tasks are called floating tasks.
All of that is not just a useless waste of time. On the contrary, having this info, can help you consider some smart moves. If a task has a total float of more than 0 and therefore not on the critical path, it can give you the freedom to move resources somewhere else where they may be more crucial. Say moving resources and the money saving bells should be ringing.
But, if your project is strapped for time and at risk of overrunning the deadline, the total float information can be used to adjust the schedule.
How do you shorten the critical path?
Because shortening the duration of a project typically also reduces its cost, shortening the critical path is often your primary goal as a project manager.
There are two ways in which you can shorten the critical path.
· You can shorten the duration of critical tasks themselves
· You can overlap critical tasks by scheduling them simultaneously.
Most of the time, you’ll do a bit of both and your Gantt Chart as well as the critical path should help you figure out the best way to do it.
The bottom line
What should be clear by now, is that the critical path of a project is a precious tool to optimise the time frame for your project, and in doing so also minimize cost and make the most of your resources.
The good news is that you don’t have to perform the calculations we explained above. Project management programs take care of this for you. In a few weeks’ time, you will be able to simply go to the ProWorkflow Gantt Chart and get it to highlight the critical path for you.