Guide to Critical Path Method (CPM)

Use the Critical Path Method (CPM) to manage large projects efficiently
By Sue-Lynn Carty

CPM project management is a technique that allows the project manager to effectively plan a large and complex project from start to finish. By performing a critical path analysis, the project manager lays out which activities are "critical" and need to be completed before any other activities on the project can begin. Critical path method scheduling helps the project manager keep the project on time and on budget.

Every CPM analysis begins with a schedule. Completing this schedule, especially on large projects with many different activities, is easiest when using critical path method software. CPM software completes project time lines and CPM diagrams allow the project manager to determine:

1. Which activities employees must complete before other activities can begin. The critical path method software translates these inputs into an activities diagram.

2. What activities employees can perform simultaneously. CPM in project management is all about cost and time effectiveness.

3. The calculations of the earliest start and latest start and end times of each activity with CPM software. No matter how efficient the critical path method aims to be, there are always circumstances out of the project manager's control that may cause delays to the start of an activity.

Action Steps

The best contacts and resources to help you get it done

Classify the critical path method Identifying the 'critical path' in your CPM diagram gives you and your staff a definitive start date and a definitive end date. The 'critical path' is the path that has the longest time line from the beginning to completion of the entire project.

I recommend: Identify the critical path for your project with CPM programs from Guy Software and Mindjet Corporation.

Develop a crash action plan or critical path analysis A crash action plan in the critical path method is a necessary contingency plan in case the deadline is unexpectedly changed. Critical path analysis will help you prepare for tasks that need to be included in a project. To prepare for such occasions, complete the 'dummy activities' section available in most critical path software.

I recommend: Stand by Soft Ltd. and the Microsoft Corporation offer comprehensive CPM project management software.

Determine float activities in CPM management There are two basic types of float activities in critical path method scheduling, free float and interfering float. Free float activities have room for delay, but their delay doesn't effect the completion of other activities. A delay in interfering floats cause delays in other activities and therefore, a delay in the total project.

I recommend: Look to Shared Plan Software Inc. and Phoenix Project Management Systems for critical path method scheduling software.

Tips & Tactics

Helpful advice for making the most of this Guide

When attempting to change the critical path method of a project (like shortening or extending time deadlines), be sure to change all the activities within the project and not just the critical path activities. If not all the activities are changed, the critical path will not change, it will just move from activity to activity until all of them are updated to reflect the new time constraints or extensions.