Slack and Costs in MS PROJECT 2019 / Online


today I will show you relation between Slack and Costs using MS PROJECT 2019 / Online.

First I will create new Project


and some Resources:


Finally, I will assign Resources to Tasks:


Using Format Tab, I will show Critical Tasks, and Slack:


OK. What is Critical Path (Task are marked red!)? It is path in which, if any activity will be late, the whole Project will be late, e.g. Project finish date will be “damaged”!

On the other hand, slack is amount of time which I have in some path, when Tasks can be delayed without jeopardizing Project finish date!

So, as you can see, all Tasks on Phase 1 are on critical path, and this path determines the duration of the Project, and Finish date (9 days Duration, and Finish date is 26.03.2020)

On the other hand Phase 2 has slack 3 days (6 days Duration, and Finish date is 23.03.2020).

Let me show you Costs. To do that, I will apply Cost Table:


As you can seem Total Cost of Task 6 is $14.400. This is because, Task 6 has Duration = 3 days, and Jim is going to work 8 hours per day, e.g. 3 Days * 8 hours / Day = 24 hours! Since cost per hour for Jim is $600, Total Cost for Task 6 is 24 hours * $ 600 = $ 14.400

Now, let’s say that Task 6 will last 5 Days instead of 3 Days:


As you can see, Project Finish date remains the same (e.g. 26.03.2020), Phase 1 will finish 2 days later (e.g. 25.03.2020), and Finish date is not jeopardized .

BU! Let’s say Cost Table again:


As you can seem Total Cost of Task 6 is now $24.000. This is because, Task 6 has Duration = 5 days, and Jim is going to work 8 hours per day, e.g. 5 Days * 8 hours / Day = 40 hours! Since cost per hour for Jim is $600, Total Cost for Task 6 is 40 hours * $ 600 = $ 24.000.

So, when you have a Slack, it means that some Task can last longer without “moving” Project Finish date, but it doesn’t mean that Cost are going to remain the same.

And, for the end of this post, lets, say that Task 6 will have 9 days Duration:


Now, Critical path is changed, so all Tasks at Phase 2 are on it. Project Duration is 12 days, and Finish Date is determined by Phase 2 (e.g. 31.03.2020). And Phase 1 has Slack 3 days!

To conclude, lot of people think that if you have a Slack than you are in a “comfort zone”. It is not a case!



About Nenad Trajkovski

Location: Zagreb, Croatia Occupation: Project Manager Interests: Project Management and MS PROJECT He was born in Zagreb, Croatia at 1963. After completing his college he started working on projects in different business areas (banking, manufacturing, automotive industry, distribution, oil companies, etc.) developing and implementing ERP systems into different companies. He has got a lot of experience working with people in different business processes and also possesses great knowledge in information technologies and financial services. Today he works as a business consultant, adn Project Manager in PERPETUUM MOBILE d.o.o. Zagreb. He is a regular lecturer for Project Management in MS Innovation Center in Varaždin, Logosoft Sarajevo in Bosnia and Herzegovina and SEAVUS GROUP in Skopje Macedonia. He was named the best lecturer of WINDAYS 2008 while his lecture was also voted as the best. In addition, he was in TOP 10 lecturers at the MS SINERGY 2009 and MS VISIA 2009, 2010. Shares first place as the best lecturer of KulenDays 2009 and 2010 and PMI Conference 2009 in Zagreb. He is also a regular lecturer in the MS Community. He is a Certified Accountant and a PMP (Project Manager Professional) and a PMI-RMP (Risk Manager Professional), MCP, MCT, and Microsoft Certified Technical Specialist - Microsoft Project 2010. From 01.01.2012 awarded with MVP (Microsoft Most Valuable Proffesional - Microsoft Project)!
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