> ## Documentation Index
> Fetch the complete documentation index at: https://docs.glidepathcpm.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Critical Path

> How GlidePath identifies and displays the critical path through your schedule

# Critical Path

The critical path is the longest chain of dependent tasks from project start to finish. Any delay to a task on the critical path delays the entire project by the same amount. GlidePath calculates and highlights the critical path automatically every time the schedule changes.

## Feature Spec Reference

**Module 3.3 -- Critical Path Visual Treatment**\
**Module 3.2 -- Backward Pass**

## What Makes a Task Critical

A task is on the critical path when its **total float is zero** -- it has no scheduling flexibility. If you move it even one day later, the project end date moves the same amount.

Total float is calculated as:

```
Total Float = Late Start - Early Start
           = Late Finish - Early Finish
```

Any task where this equals zero is critical.

## Visual Indicators

GlidePath uses color coding to distinguish critical from non-critical tasks:

| Visual                    | Meaning                                          |
| ------------------------- | ------------------------------------------------ |
| **Red task bar**          | Task is on the critical path (zero float)        |
| **Blue/default task bar** | Non-critical task (has float available)          |
| **Red dependency line**   | Link connecting two critical tasks               |
| **Float column value**    | Numeric days of float displayed in the task list |

### Enabling the Float Column

To see exact float values:

1. Click **Columns** in the Gantt toolbar
2. Check **Float**
3. Each task row shows its float in days

Green float values indicate scheduling flexibility. Zero or negative values indicate the task is critical or over-constrained.

## How CPM Calculates the Critical Path

GlidePath runs a two-pass CPM algorithm every time the schedule changes:

### Forward Pass (Earliest Dates)

Starting from the project start date, GlidePath calculates the **earliest start** and **earliest finish** for every task:

* Each task's earliest start is the latest finish of all its predecessors (plus any lag)
* Each task's earliest finish = earliest start + duration

### Backward Pass (Latest Dates)

Working backward from the project end date, GlidePath calculates the **latest start** and **latest finish** for every task without delaying the project:

* Each task's latest finish is the earliest latest start of all its successors (minus any lag)
* Each task's latest start = latest finish - duration

### Float Calculation

Float = Latest Start - Earliest Start (same as Latest Finish - Earliest Finish). Tasks with zero float form the critical path.

## Multiple Critical Paths

Complex projects often have more than one critical path -- several chains of tasks that all drive the project end date simultaneously. GlidePath highlights all of them in red. This is normal and expected in large schedules.

## Near-Critical Tasks

Tasks with small float values (1-3 days) are near-critical and deserve attention even though they are not technically on the critical path. Use the **Float** column to identify them and monitor them during project execution.

## Critical Path and Constraints

Constraints interact with the critical path:

* A **Must Start On** or **Must Finish On** constraint forces a task to specific dates, which can create or eliminate float on connected tasks.
* **Start No Earlier Than** constraints can shift the critical path by delaying a task's earliest possible start.

See [Constraints Deep Dive](/scheduling/04-constraints-deep-dive) for full detail on how each constraint type affects scheduling.

## Screenshot

<img src="https://mintlify.s3.us-west-1.amazonaws.com/glide-path/assets/screenshots/03-04-full-gantt-chart-with.png" alt="Gantt Chart with Critical Path Highlighted" />

*Gantt chart with critical path tasks shown in red and non-critical tasks in blue.*

***

## Next Steps

* [CPM Fundamentals](/scheduling/01-cpm-fundamentals)
* [Viewing and Editing Dependencies](/dependencies/03-viewing-editing)
* [Constraints Deep Dive](/scheduling/04-constraints-deep-dive)