How to Find the Critical Path

A step by step guide to finding the critical path in any project schedule. Covers building the network diagram, running the forward and backward pass, calculating float, and identifying the longest path.

By ClickUp Editorial Team·Staff Writers at ClickUp

Updated May 6, 2026

Key Insight

The critical path determines the shortest possible project duration. Focus management attention on zero float tasks because any delay to them delays the entire project. Tasks with positive float provide scheduling flexibility that can be used for resource leveling and risk management.

Before You Start

Finding the critical path requires two inputs: a complete list of tasks with estimated durations and the dependency relationships between them. If either is missing, the analysis will be incomplete. Build these from your work breakdown structure before starting the steps below.

Most project management tools (ClickUp, MS Project, Primavera) calculate the critical path automatically when you enter tasks and dependencies. The steps below explain the manual calculation so you understand what the tool is doing and can verify its output.

How to Find the Critical Path in 8 Steps

1 List All Tasks and Durations
2 Define Dependencies
3 Draw the Network Diagram
4 Run the Forward Pass
5 Run the Backward Pass
6 Calculate Float for Each Task
7 Identify and Highlight the Critical Path
8 Monitor and Recalculate During Execution

List All Tasks and Durations

Start with your WBS. List every task with its estimated duration in consistent units (days or hours). Assign a unique ID to each task. Do not include milestones in this list (they have zero duration and are added as markers after the path is calculated).

Define Dependencies

For each task, identify its predecessors: which tasks must finish before this one can start. Record dependencies as finish to start by default. Note any start to start or finish to finish relationships. The result is a dependency table with columns for Task ID, Task Name, Duration, and Predecessors.

Draw the Network Diagram

Arrange tasks in sequence from left to right based on their dependencies. Each task is a node (box) with its ID, name, and duration. Arrows connect predecessors to successors. Tasks with no predecessors start at the left. Tasks with no successors end at the right. Parallel tasks (no dependency between them) are drawn on separate rows.

Run the Forward Pass

Starting from the left, calculate the Earliest Start (ES) and Earliest Finish (EF) for each task. The first task's ES is 0 (or Day 1). Its EF is ES plus duration. For subsequent tasks, ES equals the latest EF among all predecessors. EF equals ES plus duration. When two paths merge at a task, take the later (larger) EF. Continue until you reach the final task. Its EF is the earliest possible project completion date.

Run the Backward Pass

Starting from the right (the final task's EF becomes its LF), calculate the Latest Finish (LF) and Latest Start (LS) for each task working backward. LS equals LF minus duration. For tasks that feed into multiple successors, LF equals the earliest LS among all successors. Continue until you reach the first task.

Calculate Float for Each Task

Total Float = LS minus ES (or equivalently LF minus EF). Tasks with zero float are on the critical path. They cannot be delayed without delaying the project. Tasks with positive float have schedule flexibility. Record the float for every task in the dependency table.

Identify and Highlight the Critical Path

Trace the sequence of zero float tasks from project start to project end. This is the critical path: the longest chain of dependent tasks that determines the project's minimum duration. There may be multiple critical paths if two or more chains have the same total duration. Highlight all critical paths in your network diagram and Gantt chart.

Monitor and Recalculate During Execution

The critical path is not static. Recalculate as tasks complete and actual durations replace estimates. If a non critical task consumes all its float, it becomes critical. If a critical task finishes early, a different path may become critical. Update the analysis at every major milestone or whenever significant schedule changes occur.

Enter tasks and dependencies in Gantt View and let ClickUp calculate the critical path automatically.

Map Critical Paths in ClickUp

Common Questions About How to Find the Critical Path

Can I find the critical path without project management software?

Yes. The forward and backward pass can be done manually on paper or in a spreadsheet for projects with up to 30 to 40 tasks. For larger projects, software is more practical because it recalculates automatically when durations or dependencies change.

How often should the critical path be recalculated?

Recalculate at every major milestone, whenever a critical path task finishes significantly ahead or behind schedule, and whenever dependencies or scope change. For fast moving projects, weekly recalculation is standard. The critical path can shift during execution as actuals replace estimates.

What should I do when the critical path is longer than the deadline?

Two schedule compression techniques are available. Crashing adds resources to critical path tasks to reduce their duration (costs more money). Fast tracking overlaps tasks that were previously sequential (increases risk). Both shorten the critical path but come with tradeoffs.