The Critical Path Method (CPM) is a project modeling technique developed in the late 1950s that identifies the longest sequence of tasks that determine the minimum project duration. It involves specifying activities, drawing a network diagram, performing forward and backward passes to determine early and late start/finish times, and calculating slack time to identify critical tasks that have zero float. The critical path is crucial for project management, as any delay in its tasks will result in a project delay.

1. Critical Path
Vazi Okhandiar, PMP, MCT, MBA, MSCS, BSEE
NR Computer Learning
Center
1835 W. Orangewood, #200
Orange . CA 92868
(714) 505-3475
www.nrclc.com

2. Critical Path Method (CPM)
 The critical path method is a project modeling
technique developed in the late 1950s by Morgan
R. Walker of DuPont and James E. Kelley, Jr. of
Remington Rand. - Wikipedia

3. Critical Path
 The critical path method was examined by the
United States Navy, and established a version in
1958 called a PERT (Program Evaluation and
Review Technique) analysis. PERT claimed to
reduce project management time by up to 42
percent, and was first used in the development of
the Polaris missile.
Ref: http://www.ehow.com/about_4703555_whatcritical-path.html#ixzz2igTEV3Q7

4. Critical Path
 A Critical Path is the path with the least amount of
float or slack time. A float time is the amount of
time that an activity can be delayed without
delaying the project.
 A Critical Path is the longest amount of time it will
take to complete the project.
 A Critical Path usually has 0 float but may have
negative float if the end task is constrained to an
early finish date.
 If any of the task identified in the critical path is
late, then the project will be late.

5. 6. Steps for identifying Critical
Path
1.
2.
3.
Specify the activates, duration and dependencies
Draw a network diagram.
Perform the forward pass to identify all Early Start and Early
Finish times for the network.
Early Finish = Early Start + Duration
4.
Perform the backward pass to identify all Late Start and Late
Finish times for the network.
Late Start = Late Finish – Duration
5.
Calculate the slack time.
Float = Late Start (LS) – Early Start (ES)
6.
Identify the task on critical path with 0 float (slack) time.

6. 1. Task/Duration/Predecessor
TAS
K
A
B
C
D
E
F
G
Duratio Predecess
n
or
2
---2
A
1
A
3
A
1
C,D
3
B
2
E,F

7. Terminologies
 ID – Task ID
 D- Duration
 ES – Early Start
 EF – Early Finish
 LS – Late Start
ES
 LF – Late Finish
F ID DR
LS
LF
 S - Slack
EF

8. 2. Network Diagram
B 2
F 3
Activity
A 2
C 1
G 2
Duratio
n
ES
D 3
E 1
F
LS
EF
ID DR
LF

9. 3. Forward Pass
2
Early
Start
4
B 2
1st
2
A 2
7
F 3
Early
Duration=
9days
Finish
2
5
D 3
7
3
C 1
2
0
4
5
task starts at 0
EF = ES + DR
ES = EF of predecessor
When more than one predecessor, pick the
larger #
6
E 1
9
G 2
ES
F
LS
EF
ID DR
LF

10. 4. Backward Pass
2
4
B 2
1st task should
end with LS = 0.
2
0
2
A 2
0
2
Late
Start
2
4
4
7
F 3
4
7
7
9
G 2
7
9
3
C 1
5
6
Late
Finish
2
LS = LF - DR
LF = LS of successor
5
D 3
3
6
5
6
E 1
6
7
When more than one successor, pick the
smallest #
ES
F
LS
EF
ID DR
LF

11. 5. Slack / Float
2
4
0 B 2
2
4
0
2
0 A 2
0
2
4
7
0 F 3
4
7
7
9
0 G 2
7
9
2
3
3 C 1
5
6
Float = LS – ES
2
5
1 D 3
3
6
5
6
1 E 1
6
7
Float = Late Start (LS) – Early Start (ES)
ES
F
LS
EF
ID DR
LF

12. 6. Critical Path
The path with 0 Float
is the critical path.
0
2
0 A 2
0
2
2
4
0 B 2
2
4
4
7
0 F 3
4
7
A-B-F-G is the critical
5
path. 6
0 C 1
5
6
2
5
0 D 3
2
5
LS = LF - DR
LF = LS of successor
7
0 G 2
7
5
6
1 E 1
6
7
9
9
ES
F
LS
EF
ID DR
LF

13. Thank You!
Vazi Okhandiar, PMP, MCT, MBA, MSCS, BSEE
NR Computer Learning Center
1835 W. Orangewood, Suite 200
Orange, CA 92868
www.nrclc.com . (714) 505. 3475
info@nrclc.com