PERT Calculator

This PERT calculator can be employed for swift computation of the likelihood of your project being completed within the desired timeframe, on the basis of the Program Evaluation and Review Technique (PERT).

The Program (sometimes Project) Evaluation and Review Technique, frequently shortened to PERT, is a way of analyzing the tasks required to complete a specific project, particularly the time each task requires, and to identify the minimum time required for completion of the whole project. PERT is most frequently employed for research projects when the length of any specific activity cannot be predicted, and so work is planned around a series of milestones.

PERT Analysis Calculator


How to Use the Calculator

Step 1: Critical path task identification.

This is the longest potential time that will be needed to progress from start to finish. This will calculate the full length of time needed to complete a project and so any delays which arise on this pathway will postpone reaching the finishing event by the length of that delay at a minimum.

Step 2: Input your time estimates:

Optimistic: The shortest possible time needed to complete a task, on the assumption that everything progresses more swiftly than standard expectations.

Most Likely: The most probable length of time needed to complete a task, on the assumption that everything proceeds in line with standard expectations.

Pessimistic: The longest length of time needed to complete a task, on the assumption that everything that can go wrong, does go wrong.

For adding a new critical path task to the data table, click the "+ Add" button.

Step 3: Click the calculate button to view your results.

The PERT calculator will provide you with a table with the data below.

1. PERT Expected Time: a probability calculated on the basis of likely duration. This is a best estimate of how long a particular task will take, on the assumption that matters proceed in a standard fashion (this expected time being the average time that would be produced if this task were to be replicated numerous times over a long period).
Formula: Expected Time = (Optimistic Time + 4 × Most Likely Time + Pessimistic Time) / 6

2. Standard Deviation: the average amount of deviation from the time estimates, depending on whether things go well or badly.
Formula: Standard Deviation = (Pessimistic Time – Optimistic Time) / 6

3. Variance: the value spread across a standard distribution.
Formula: Variance = (Standard Deviation) 2

Step 4: Input the amount of time you wish the project to take to check how likely it is that you will meet this target.

The probability of finishing the project within a specified time is calculated using the following basic formula:

Formula: Z = (Td − ∑te) / (∑V)0.5


Z = Number of standard deviations of the normal distribution,

Td = Desired completion time for the project,

∑te = Expected completion time for the project,

∑V = Sum of the variances along the critical path.


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