While dealing with some projects, it is a must to have proper project management. Project scheduling is one of the important aspects of project management, in which, one has to list all the milestones, activities, etc for some projects, with the start date and the end date, with a sequence that can lead to effective execution.
We are not going to go into the details of aspects of project management, but in this article, we are going to understand the difference between free slack, and total slack.
Free Slack Vs Total Slack
What is Slack?
For someone who is not already familiar with the term “Slack”, let’s first try to discuss what is Slack. Don’t worry, since this is going to be a quick discussion on Slack. So, Slack is a term used in the project management process. Slack is also called Float (or Total Float), and it is the amount of time by which a task can be delayed, without affecting the project completion time.
So, I think you have understood about the term “Slack”, and now it is somewhat easy to understand what is Free Slack, and what is Total Slack since these are some types of Slack. We will now move towards understanding what is Free Slack, and Total Slack, and we will find out some points of differences between them.
Free Slack Vs Total Slack
As mentioned earlier, In project management, project scheduling is one of the very important tasks. Slack (also called float) is the amount of time some task can slip before it bumps into another task. You can use it as a buffer time whenever needed if your task is at risk of delay. In other words, we can say that slack is the time by which, you can delay a task, without interfering with another task.
There are two types of Slack – Free Slack, and Total Slack. Here, we are going to understand what we mean by Free slack, and what we mean by Total slack, and also we would understand what is the difference between free slack and total slack.
Comparison between free slack and total slack can show how these terminologies differentiate from each other, and what they mean. It becomes important to understand when you are part of some project or someone who needs to handle the project. Here is a quick table for understanding the difference between Free Slack and Total Slack.
| Free Slack | Total Slack |
|---|---|
| The time by which an activity can be delayed without impacting the following activity. | The time by which an activity can be delayed without impacting the project finish date. |
| Free Slack = ES(Early Start) of Successor – EF(Early Finish) of current activity. | Total Slack = LS(Late Start) – ES(Early Start) OR Total Slack = LF(Late Finish) – EF(Early Finish). |
| Activity-based flexibility, delaying an activity without delaying the successor’s early start date. | Project-level flexibility, delaying an activity without impacting the project finish date. |
| Also known as ‘Free Float’. | Also known as ‘Total Float’. |
| A task with zero Free Slack is considered critical; any delay affects the project finish date. | Total Slack can be negative (behind schedule) or positive (the activity can be delayed without affecting the project finish date). |
Here is a quick walkthrough of the differences –
1. Difference Between Free Slack and Total Slack
What is Free Slack?
Free slack for some activities can be simply defined as the time, by which we can delay the activity, without causing any impact on the following activity.
In other words, we can define total slack as – “It is the amount of time in which we can delay the scheduled activity, without delaying the following activity”
What is Total Slack?
The total slack of an activity can be simply defined as the time, by which the activity can be delayed, without having an impact on the finish date of the project.
In other words, we can define Total Slack as – “It is the amount of time in which scheduled activity can be delayed or expanded from its starting date without delaying the project finish date or violating a scheduled constraint”
2. Total Slack and Free Slack Formula
Now, that we are quite familiar with what we mean by the free slack and total slack, let’s try to have a look at the formula to calculate the free slack and total slack.
Formula to calculate free slack(free float) –
We can calculate the free slack (or free float) by subtracting the early finish date of the current activity, from the early start of the next activity.
So, here is the formula to calculate the free slack –
Free Slack = ES(Early Start) Of Successor – EF(Early finish) of current activity.
Formula to calculate Total Slack :
The total slack can be calculated by subtracting the early start date of the activity, from its last date. We can also get the total slack by subtracting the early finish date of the activity from its late finish date.
Total Slack = LS – ES
OR
Total Slack = LF – EF
Note: Here ‘LS’ indicates a late start date, while ‘ES’ indicates to early start date. Same way ‘LF’ indicates to late finish date, while ‘EF’ indicates to early finish date.
3. In Terms of Flexibility
Free Slack:
When we need to discuss flexibility then Free Slack is the activity-based flexibility, wherein the amount of time you can delay the current project activity, without delaying the successor project’s early start date.
Total Slack:
Total Slack gives project-level flexibility, which means here activity may be delayed without delaying the project finish date.
4. Free Slack Other Name
Free Slack:
Free Slack is also known as a ‘Free Float’.
Total Slack:
In another way, Total Slack is well known as a ‘Total Float’.
5. Manner
Free Slack:
A task with zero Free Slack or Float is considered to be a critical task, in that case, if a critical task goes delayed then the project finish date will also be delayed.
Total Slack:
Total Slack can be either negative or positive, here if the Total Slack is negative that means the project is behind schedule. If Total Slack is positive then it shows that the amount of time for the activity can be delayed without delaying the project finish date.
Conclusion
In this article, we have seen about Free slack and total slack. We have also seen some points of differences related to Free slack and Total slack. We hope that you have got a clear idea about free Slack and total Slack.
We hope that you have got a clear idea about the free slack and total slack. If you find the information helpful, please consider sharing the information with other people. Thank you for being with us!
Frequently Asked Quiz Questions About Free Slack Vs Total Slack
Ans: Yes it is true.
Ans: Yes.
Ans: Free Slack.
Ans: Total Slack.
Ans: If Total Slack is negative then it indicates that the project is behind schedule.
Ans: When the total slack is positive, it means that we can delay the task by some time.
