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Project Managers: Copy This Critical Path Example to Excel (16 Days)

Isometric critical path network illustration

The critical path is the longest chain of dependent tasks in a project, and it sets the minimum time the whole project can take. In the worked example below, five tasks connect into a sequence with a total duration of 16 days, and every task on that chain carries zero float, meaning any delay pushes the finish date back by the same amount. The sections that follow walk through the forward pass, the backward pass, the diagram, and how to build the same calculation in a spreadsheet.

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Table of Contents

What Does a Critical Path Example Look Like in Practice?

Every critical path calculation starts with a task list. You need each task’s duration and which tasks must finish before it can start. Here is a five-task example you can reproduce in any spreadsheet, structured the same way a small software rollout or office move might look on paper.

Task ID Task Name Duration (days) Predecessors
A Requirements gathering 3 None
B System design 5 A
C Content preparation 4 A
D Development 6 B
E Testing and rollout 2 D, C

Five tasks, five durations, and a couple of dependency branches. That’s enough complexity to show how convergence points work, without burying the math.

Running the forward pass

The forward pass calculates the earliest start (ES) and earliest finish (EF) for each task, moving left to right through the network. Task A has no predecessor, so its ES is day 0. Its EF is ES plus duration: 0 + 3 = 3.

From there, each task’s ES equals the EF of whichever predecessor finishes latest.

Task E depends on both D and C. D finishes at day 14, C finishes at day 7. E can’t start until the slower of the two wraps up, so its ES is 14, not 7. That single line is where most people miscalculate a critical path: they average the two predecessors, or they take whichever one appears first in the table, instead of taking the later finish. A worked classroom example using the same method shows this convergence rule producing a critical path of ABDEG with a 16-hour total, the same structural logic scaled to a different time unit.

Running the backward pass

The backward pass works in reverse, calculating latest finish (LF) and latest start (LS) without pushing the project past its forward-pass end date of day 16. Start at the last task and work backward: E’s LF equals the project’s total duration, 16. Its LS is LF minus duration: 16 – 2 = 14.

Notice task C: its LF is 9, not 7. It has two days of breathing room because task E waits for task D anyway.

Calculating float and finding the critical path

Float, sometimes called slack, is LS minus ES. A task with zero float has no room to slip without delaying the whole project.

Tasks A, B, D, and E all carry zero float. That chain, A to B to D to E, is the critical path, and it runs the full 16 days. Task C has two days of float. It can start up to two days late and still not touch the project’s finish date, which is exactly why it doesn’t belong on the critical path even though it’s a real task with real deadlines attached.

Critical path with task float

How Do Forward and Backward Pass Calculations Actually Work?

The formulas behind ES, EF, LS, and LF are simple on paper and easy to fumble in practice. EF equals ES plus duration when you’re counting continuous time (hours, or days measured as elapsed time). But when tasks are counted inclusively, meaning day 1 of a task is a whole calendar day rather than a zero point, the formula shifts to EF = ES + duration – 1.

Here’s why that one detail causes so many scheduling errors. Say a task starts on day 5 and lasts 3 days, counted inclusively. Without the adjustment, you’d calculate EF as day 8. But day 5, 6, and 7 are the three days of work, so the correct EF is day 7. Skip that subtraction across a ten-task chain and the whole project timeline drifts a day longer than it should, task by task, until the final date is meaningfully wrong. This inclusive-counting nuance rarely gets mentioned in textbook explanations of the critical path method, but it’s one of the most common reasons a manually built schedule doesn’t match what a scheduling tool produces.

Float works the same way regardless of which counting convention you use: LS minus ES, or equivalently LF minus EF. Zero float is what defines the critical path, full stop. Any task with float greater than zero has some cushion. Any task at zero is a bottleneck.

Multiple critical paths happen more often than beginners expect. If two separate chains through the network both add up to the same total duration, you get two (or more) critical paths running in parallel. This matters for risk management, because a project with a single critical path only needs contingency planning around one sequence of tasks. A project with two or three parallel critical paths needs contingency around all of them simultaneously, since a delay on any one of them delays the finish date. Critical Path Analysis literature also introduces the concept of critical path drag: the amount of time a specific critical-path task is adding to the overall project length, which helps prioritize which task to shorten first when you’re deciding where to spend compression effort.

Convergence points, where a task waits on two or more predecessors, are frequent locations for the critical path to run through, since the network is forced to wait for whichever branch finishes slowest.

How Do You Draw a Critical Path Diagram and Gantt Chart?

A network diagram (also called a PERT diagram) turns the task table into nodes and arrows. Each box represents a task, and the arrows show dependency direction. Building one from the example above and putting it into a Gantt chart in Excel takes about six steps:

  • Draw one box per task, labeling each with the task name and duration.
  • Draw arrows from each predecessor to its successor, following the dependency column in your task table.
  • Add four small labels inside or beside each box: ES and EF on top, LS and LF below.
  • Circle or shade the boxes connected by zero float. That visual chain is your critical path.
  • In Excel, list tasks down a column, add a start-date column using a formula referencing each task’s ES value, then insert a stacked bar chart to build the Gantt.
  • Apply conditional formatting so any task with float equal to zero automatically fills a different color, which keeps the critical path visible even after you add more tasks later.

That conditional formatting step is worth doing early. Once a project schedule grows past 20 or 30 tasks, spotting the critical path by eye becomes unreliable, and a color rule tied to your float column catches it automatically every time you update dates. Atlassian’s own walkthrough of the critical path method makes a similar point: viewing the network diagram and the Gantt side by side helps you see exactly which parallel branch is holding up the finish date, something that’s hard to catch from the diagram alone.

If you’re building your task list from scratch rather than starting with dependencies already mapped out, a work breakdown structure is the right starting point before you attempt any forward pass.

When Should You Crash or Fast Track a Schedule?

Two techniques shorten a critical path once you’ve identified it: crashing and fast tracking. Crashing means adding resources to a critical task to shrink its duration, like putting a second developer on task D above to cut it from 6 days to 4. Fast tracking means overlapping tasks that were originally sequential, starting task E’s early testing work before task D fully finishes, instead of waiting for a clean handoff.

Both work, and both carry real trade-offs:

  • Crashing usually increases direct cost, since extra people or overtime hours aren’t free.
  • Fast tracking increases coordination risk and rework, since work started on incomplete inputs sometimes has to be redone.
  • Either technique applied to a non-critical task (like task C in the example, which has two days of float) does nothing for the project finish date and just burns budget.

Rank your critical-path tasks by potential time saved per dollar spent, and act on the best candidates first rather than compressing everything at once. That’s the approach TeamGantt’s guidance on the critical path recommends, and it holds up: crashing the wrong task, or crashing every task equally, tends to increase cost far more than it shortens the schedule.

Pro Tip: Before you crash a single task, calculate its cost-per-day-saved and compare it against every other critical-path task. The cheapest day of schedule reduction is rarely the first task you’d guess.

What Are the Most Common Critical Path Mistakes?

Most critical path errors trace back to bad inputs, not bad math. Missing a dependency, guessing at a duration instead of using historical data, or ignoring a near-critical chain that’s one delay away from becoming the critical path: these mistakes are far more common than a broken formula.

A short checklist to run before you trust any critical path calculation:

  1. Confirm every dependency is captured, especially soft dependencies that aren’t in your project management tool by default.
  2. Double check durations against past project data rather than optimistic estimates.
  3. Identify near-critical tasks (low float, not zero) and watch them as closely as the critical path itself.
  4. Track critical-path tasks daily during execution, not just at the planning stage.
  5. Report schedule risk to stakeholders using actual float numbers, not general impressions of how things are going.

That last point matters more than it sounds. Telling a sponsor “we’re a little behind” invites debate. Telling them “task D has zero float and slipped one day, which moves the finish date to day 17” ends the debate and starts the conversation about what to do next. For more on communicating this kind of risk clearly, project quality and communication management covers how to frame schedule status for different stakeholders.

An Editorial Note on Learning the Critical Path Method

An Editorial Note on Learning the Critical Path Method — overview diagram

Most people who struggle with critical path calculations aren’t struggling with the concept. They’re struggling with the mechanics: which predecessor to take at a convergence point, whether to subtract one for inclusive counting, where float actually comes from. That’s why a worked example, done by hand at least once, teaches more than a dozen articles explaining the theory.

The value of the exercise above isn’t the 16 day answer. It’s building the habit of tracing every dependency back to a number before trusting a schedule. Readers who want more structured practice with these calculations, along with the broader scheduling and process control skills that surround them, can work through the free project management practice test as a next step, and pair it with the Critical Path Method guide for a deeper walkthrough of monitoring techniques.

— David Lovell

Build These Scheduling Skills Into a Formal Credential

A worked example teaches you the mechanics. A certification proves you can apply them under real project constraints, which is the gap between knowing the formulas and getting hired to run the schedule. Management and Strategy Institute’s Six Sigma Certification covers process control and project scheduling fundamentals that build directly on the critical path skills above, at one all-inclusive price with no separate exam fee tacked on later.

Lean Six Sigma Black Belt Certification

For readers who want to go further into advanced process improvement and project leadership, the Lean Six Sigma Black Belt Certification adds deeper statistical and project control methods on top of the fundamentals. Both programs are self-paced, so you can work through the material on your own schedule rather than a fixed classroom calendar. If you want the complete study package bundled together, the certification course package includes the training materials and exam attempt in one purchase. Start with whichever course matches where you are in your career, and work the practice questions the same way you worked the task table above: one calculation at a time.

Sources

FAQ

Can you give an example of critical path analysis?

Yes: a five-task project with requirements, design, content prep, development, and testing produces a critical path of A, B, D, E with a total duration of 16 days, while a parallel task (content preparation) carries two days of float and sits off the critical path.

How do you calculate the critical path?

Run a forward pass to find each task’s earliest start and finish, then a backward pass to find the latest start and finish, then subtract LS minus ES for every task. Any task where that result is zero sits on the critical path.

What does critical path mean in project management?

The critical path is the longest sequence of dependent tasks in a project, and it determines the shortest possible time the entire project can take, since any delay on a zero float task pushes the whole finish date back.

How do you build a critical path in Excel?

List your tasks with durations and predecessors, calculate ES, EF, LS, LF, and float in separate columns using simple addition and subtraction formulas, then apply conditional formatting to highlight rows where float equals zero.

Can a project have more than one critical path?

Yes, if two or more task chains add up to the exact same total duration, the project has multiple critical paths running in parallel, and each one needs its own contingency planning since a delay on any of them delays the finish date.