Free Float Vs Total Float

What is Total Float?

Total float is the amount of time an activity can be delayed without delaying the project finish date or a controlling finish constraint. PMI defines it as the delay allowed from the early start without affecting project completion, and Oracle Primavera describes it as the maximum delay that does not push the project finish date or another scheduling constraint. 

This is why total float PMP questions often appear in critical path problems. It helps you identify which activities have room to move and which do not.

Definition and Formula

You can calculate total float in either of these two ways:

• TF = LF − EF
• TF = LS − ES

Both formulas yield the same answer because they compare early and late dates for the same activity. PMI states both forms directly in its scheduling guidance.

Relationship to the Critical Path

An activity with TF = 0 is critical. That means it has no flexibility in its schedule. If it slips, the project's finish date slips too, unless something else changes in the network. PMI notes that the chain of zero-float activities forms the critical path, and that a schedule can have multiple critical paths.

So, when learners study total float and free float, total float is usually the first number they use to spot critical work.

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What is Free Float?

Free float is the amount of time an activity can be delayed without delaying the early start of any immediate successor activity. That is the local view of schedule flexibility. It does not ask, “Will the whole project finish late?” It asks, “Will the next task have to start late?” PMI and Oracle use nearly the same definition here.

This is why free float project management questions often focus on task relationships rather than the entire project.

Definition and Formula

The usual free float formula is:

• FF = ES of next activity − EF of current activity

If there is more than one immediate successor, you use the lowest early start among those successors. PMI states this explicitly in its scheduling terminology. 

When Free Float Exists

Free float exists when an activity can finish later without delaying the early start of the next activity. In practice, it often appears in networks where there is a gap before the successor starts, or where multiple paths converge on a single successor, and one path finishes earlier than the other. PMI’s examples show that free float is based on successor early starts, not on the overall project finish.

That is the core difference between free float and total float calculations. Free float is narrower. Total float is broader.

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Free Float vs Total Float: Key Differences

Here is a simple comparison of Free Float Vs Total Float:

A quick takeaway: free float can never exceed total float. If your answer shows FF> TF, the calculation is incorrect. That quick rule is widely used in PMP® preparation because free float is only one part of the activity’s total flexibility.

Interfering Float (TF − FF)

Interfering float is the portion of total float that can be used without delaying the project finish date, but it will delay the early start of one or more successor activities. In simple words, it is the extra float left after the free float is used up.

So the formula is:

Interfering Float = TF − FF

Why does it matter? A task may look safe at the project level, but still cause trouble for downstream teams. That is why schedulers do not rely solely on total float.

Example: Calculate TF and FF

Let us take a small network:

• Activity A: duration 3
• Activity B: duration 4, after A
• Activity C: duration 2, after A
• Activity D: duration 3, after both B and C

Step 1: Forward pass

• A: ES = 0, EF = 3
• B: ES = 3, EF = 7
• C: ES = 3, EF = 5
• D: ES = 7, EF = 10

D starts at 7 because it must wait for both B and C, and B finishes later.

Step 2: Backward pass

• D: LF = 10, LS = 7
• B: LF = 7, LS = 3
• C: LF = 7, LS = 5
• A: LF = 3, LS = 0

Step 3: Calculate total float

Using TF = LS − ES:

• A: TF = 0 − 0 = 0
• B: TF = 3 − 3 = 0
• C: TF = 5 − 3 = 2
• D: TF = 7 − 7 = 0

Step 4: Calculate free float

Using the free float formula, FF = ES(next) − EF(current):

• A has two successors, B and C. Use the lower ES of the successors, which is 3.
  FF = 3 − 3 = 0
• B goes to D.
  FF = 7 − 7 = 0
• C goes to D.
  FF = 7 − 5 = 2
• D has no successor, so FF is usually taken as 0 in simple exam-style examples.

Step 5: Read the result

• The critical path is A → B → D, because all three have TF = 0
• Activity C has TF = 2 and FF = 2
• Interfering float for C is TF − FF = 2 − 2 = 0

This example shows an important point. Sometimes, free float and total float are the same. But that does not happen in every activity. It depends on the network logic and successor timing. The formulas and interpretation here match PMI’s CPM guidance for total float and free float.

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Common PMP® Mistakes and Quick Checks

Many learners lose marks not because the math is hard, but because they rush.

• The first common mistake is confusing the meanings of the two floats. Total float is about the project finish date. Free float is about the early start of the next activity. If you swap those ideas, the whole answer goes wrong.
• The second mistake is forgetting that, for free float, you use the earliest start among immediate successors. This matters at merge points and in shared-successor situations.
• The third mistake is missing the quick logic check:

FF ≤ TF

If the free float is greater than the total float, revisit the numbers. That result is not valid in standard CPM logic.

• A fourth point worth knowing is negative float. This usually appears when a schedule has a hard date or constraint that is tighter than the calculated network allows.

Oracle states that negative float can occur when a constraint or actual date creates a schedule shorter than the critical path duration, and PMI notes that negative total float means the project cannot finish at the desired time without changing logic or durations.

Key Takeaways

• Total float and free float may look similar, but they answer two different planning questions
• Once you understand free float, total float, and the free float formula, critical path questions become much easier to solve

FAQs

1. How do you make a project report step by step?

Define the purpose, collect project data, summarize progress, note milestones, risks, issues, budget, and timeline updates, then add recommendations and next steps. Organize clearly, review for accuracy, and share with stakeholders.

2. What is a project report used for in project management?

A project report is used to track progress, communicate updates, highlight risks or delays, support decision-making, and keep stakeholders informed about project scope, budget, timeline, and outcomes.

3. What’s the difference between a project report and a status report?

A project report gives a broader view of the project, including goals, performance, risks, and outcomes. A status report is usually shorter and focuses on current progress, immediate issues, and upcoming tasks.

4. What should be included in a project report?

A project report should include project objectives, scope, timeline, progress summary, milestones, budget details, risks, challenges, team performance, key findings, and recommended next steps.

5. What is the best format for writing a project report?

The best format is clear and structured: title, project overview, objectives, progress, budget, risks, challenges, outcomes, and next steps. Use headings, bullet points, tables, and concise language to make the text easier to read.