What is the difference between Free Float and Total Float?

The difference between Free Float and Total Float is one of the key concepts in project time management:

**Total Float:**
Total Float is the amount of time an activity can be delayed without delaying the project finish date. In other words, it shows how much we can delay starting an activity or extend its duration without changing the project completion date.

Formula: Total Float = Late Finish

• Early Finish OR Late Start - Early Start

**Free Float:**
Free Float is the amount of time an activity can be delayed without delaying the Early Start date of any successor activities. It indicates how much we can delay an activity without impacting the immediately following activities.

Formula: Free Float = Early Start of Successor

• Early Finish of Current Activity - Lag

**Key Differences:**

1. **Impact Scope:** Total Float considers the entire project timeline, while Free Float only considers immediately succeeding activities.

2. **Magnitude:** Free Float is always less than or equal to Total Float; it can never be greater.

3. **Critical Path:** Activities on the Critical Path have both Total Float and Free Float equal to zero.

4. **Flexibility:** Using Free Float has no impact on other activities' schedules, but using Total Float may reduce the float of other activities downstream.

**Practical Example:**
Consider Activity A with 3-day duration:


• Early Start: Day 1, Early Finish: Day 3


• Late Start: Day 5, Late Finish: Day 7


• Successor Activity B starts on Day 6

Total Float = 7

• 3 = 4 days

Free Float = 6
• 3 = 3 days

In both Primavera P6 and Microsoft Project, these values are automatically calculated and displayed, serving as important tools for resource management and activity prioritization decisions.