Difference between Project float, free float and float

What is the difference between Project float, free float and float, lot of times i see the questions are tweaked to confuse, using all the above 3 terms.


Just want to get a clear understanding.


Thank you all for the helpful information.


 

Project Float:  the cushion you provide yourself b4 committing a date to customer.  Suppose your planned schedule completion is: 15 June and you promise the customer 15 July for completion of deliverables, you are giving yourself a month more time

Free Float:  This is the amount an activity can be delayed without delaying the Early Start of subsequent activities.  This is the cushion within the activity It is calculated as LS-ES or LF-EF for any activity.  Suppose your LS=10; ES=2.  You have 8 days of tolerance/slack w/o adversely affecting the project's subsequent activities early start time

Free Float & Float are some times interchangeable.  Float is the critical path duration & Non critical path duration difference.  If there are several branches in the network diagram, each branch has its float calculated as its critical path duration - branch duration. 

e.g. Critical path A-E-F-H : 40 days

  Branch A-B-D-H: 36 days, then Float for each of the activities A, B, D, H is 40-36 = 4 days i. e. you can use this 4 days spare time and put up that much delay on any one of the A/B/D/H or any combination of activities - not to exceed 4 days otherwise you will be slipping from the schedule completion

 

Chandra

Pl. read this good article for a better explanation than I provided for Float, Free Float etc

 

http://www.deepfriedbrainpmp.com/2009/08/total-free-float-cpm-network-di...

 

Chandra

I choose to differ in the folloing example:


Given that A &H fall on the critical path , do you mean to say you can delay the start time of either A or H w/o affecting the project completion date ?? You prob might not have meant to say so, but the below extract certainly portrays it in that fashion...


 


 


"e.g. Critical path A-E-F-H : 40 days


  Branch A-B-D-H: 36 days, then Float for each of the activities A, B, D, H is 40-36 = 4 days i. e. you can use this 4 days spare time and put up that much delay on any one of the A/B/D/H or any combination of activities - not to exceed 4 days otherwise you will be slipping from the schedule completion"

Biswas rahul:


Good point and great attention to details!  I just illustrated quickly a critical path and a near critical path to bring out the float concept in quantitatively so people can understand.  Sure there is no slack on activities common to critical path & non-critical path. 


Chandra