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Do you need a slack time calculator for your project management team? Look no further. This slack time calculator will take the guesswork out of your project and make your calculation easy too.

Keep reading to learn:

  • What is slack time?
  • How to calculate the slack time (the slack time formula).
  • The importance of slack time.
  • How to use our slack time calculator.

What is slack time in project management?

Slack time or float time is a term used in project management to refer to the maximum amount of downtime or delay we can have without project failure.

Another way to explain this would be the difference between the expected and scheduled completion dates. Here, the first is when the company anticipates that they will finish the project, while the scheduled date is the one agreed upon with the customer.

We can set slack time for the entire project or different stages or parts of the project.

If the team can complete a project in two weeks, a project manager may set the time for the project to be completed as three weeks. This allows the company that is providing the service to deal with any issues that may arise during project development. So the extra week catered for in the project completion time is called slack time.

A good project manager understands the importance of slack time to the timely completion of any project.

Are you enjoying this calculator? Our lead time calculator may interest you too.

The importance of slack time in project management?

In the service industry, delivering projects on time to customers is crucial to staying in business. However, problems during development are inevitable, and we must cater for them. This is where slack time comes in. A good project manager will ensure that there is slack time to rectify any issues that may develop when he plans for a project.

Project managers monitor slack time during project development. This is because if we schedule a section of a project to be completed by the 10th of the month and it is completed one week behind schedule, there is less slack time available for completing the other parts of the project.

When slack time begins to diminish, a project manager will see this as a warning that his team may not complete the project on schedule unless adjustments are made.

For instance, diminishing slack time may signal the need for more skilled labor on the project or the need to reevaluate how the tasks are being completed.

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How to calculate Slack time – the slack time formula

To calculate the slack time (SL), we subtract the earliest possible start (EST) time from the latest possible start time (LST)

So the slack time formula is expressed as:

SL=LSTEST\small \text{SL}=\text{LST} - \text{EST}

Slack time calculation example

A project's scheduled start date is the 10th of February (the earliest possible start date), and the latest possible start date is the 23rd of February. So using the slack time formula:

ST=2310=13 days\small\text{ST} = 23 - 10 = 13 \text{ days}

So the slack time for this project is 13 days.

How to use our float time calculator

Our float time calculator is very easy to use:

  1. Simply click the calendar icon and choose the earliest possible date (EST) the project can start.

  2. Next, choose the latest possible date (LST) the project can start.

  3. You should now be able to see the slack time (ST) for the project.


What are the steps in calculating slack time for a project?

To calculate slack time for a project:

  1. Determine the earliest date your company can start the project.

  2. Determine the latest date the project can begin without going over the deadline.

  3. Subtract the start date from the end date.

  4. The resulting answer is the slack time for the project.

What does the term slack time mean?

The term slack time is used in everyday life to mean relaxation time or time when no work will be done.

However, in business, we use the term slack time to refer to the extra time we have allowed ourselves to make adjustments when we encounter issues on a project.

Slack time allows a company to deal with the inevitable problems that come up and complete the project within schedule.

Why do we need slack time?

Slack time is critical in business. We use the slack time in the following ways:

  • To deal with tasks that go over the estimated time frame;

  • Allows us to delay the start of components of a project where necessary without going over our scheduled date of completion;

  • Helps to keep a project within budget; and

  • To keep project deadlines intact.

Adena Benn
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