Free PERT Chart Maker
Diagrams & FlowsEnter tasks, durations, and what comes after what. The critical path is calculated — earliest and latest start and finish, float, and the zero-float chain highlighted for you. No signup, no watermark, free PNG export.
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How to Use
- 1
List your tasks
Each task gets a letter, a name, and a duration. A small sample project is already loaded so you can see the shape before you replace it.
- 2
Say what comes after what
Under each task, click the letters of the tasks that must finish first. The columns rearrange themselves so every arrow still points forward.
- 3
Read the critical path
The forward and backward pass runs on every change. Zero-float tasks are outlined and linked in the accent colour — that chain is your critical path, and the summary strip names it.
- 4
Rename tasks on the chart
Click any task name on the diagram and type. The figures stay calculated, so the chart cannot contradict its own schedule.
- 5
Export
Download a PNG that matches the preview 1:1 — free, no watermark. Turn the ES/EF/LS/LF rows off first if you only want the picture.
Why Choose GraphMake?
It Calculates the Critical Path — You Do Not Colour It In
Most free PERT tools are a shape library. They hand you boxes and arrows and leave you to work out which tasks are critical, then colour that chain in by hand. But finding the critical path is the job — the diagram is just how you show the answer.
So this one solves it. Enter durations and dependencies and it runs a forward pass for earliest start and finish, a backward pass for latest start and finish, and takes the difference as float. Every zero-float task is outlined automatically and the links between them are drawn in the accent colour. Change a single duration and the whole chain re-evaluates.
Reading an Activity-on-Node Box
Each box carries six numbers in the standard textbook arrangement. The top row is earliest start · duration · earliest finish. The bottom row is latest start · float · latest finish.
The one to look at is float, in the middle of the bottom row. Zero means the task has nowhere to move: start it late and the project finishes late. A float of 7 means that task could slip a week and nobody downstream would notice — which is exactly where to take resources from when a critical task is in trouble.
PERT Chart or Gantt Chart?
Use a PERT chart when the question is what depends on what — the shortest possible schedule, which tasks are critical, where the slack is. Dependencies are the structure of the diagram, so they are impossible to miss.
Use a [Gantt chart](gantt chart maker) when the question is when — real dates, overlapping bars, who is busy in March. Gantt charts show a calendar well and dependencies badly; PERT charts are the reverse. Most projects end up wanting both, at different moments.
Frequently Asked Questions
What is a PERT chart?
A PERT chart is a project network diagram: each task is a box, and arrows show which tasks must finish before others can start. Unlike a Gantt chart, which lays tasks out against a calendar, a PERT chart shows the structure of the dependencies — which is what tells you the shortest possible project length and which tasks cannot slip.
How do you find the critical path?
Run a forward pass to get each task's earliest start and finish, then a backward pass from the project end date to get the latest start and finish it could have without delaying the project. The difference is the float. Tasks with zero float form the critical path. This tool does both passes on every edit, so you never calculate it by hand.
What do ES, EF, LS and LF mean?
Earliest start, earliest finish, latest start, latest finish. The top row of each box shows earliest start, duration, and earliest finish; the bottom row shows latest start, float, and latest finish. A task with LS equal to ES has no slack — it is on the critical path.
What is float or slack?
How long a task can be delayed without pushing out the project end date. It is the gap between when a task could start and when it must start. Zero float means any delay to that task delays the whole project, which is exactly what makes the critical path worth identifying.
What is the difference between PERT and CPM?
They were developed separately and are now usually taught together. CPM (critical path method) is the scheduling arithmetic — the forward and backward passes that find the zero-float chain. PERT originally added three-point estimates for uncertain durations. The diagram both produce is the same activity-on-node network, which is what this tool draws.
Is a PERT chart the same as a network diagram?
In practice, yes — for the activity-on-node style drawn here, where each box is a task and arrows are dependencies. Some older textbooks use activity-on-arrow, where the arrows are the tasks and the nodes are milestones. Activity-on-node is what nearly every modern course and PM tool uses.
Can two tasks be on the critical path at the same time?
Yes. If two parallel chains take exactly the same time, both have zero float and both are critical — delaying either one delays the project. Every zero-float task is outlined on the chart; the summary strip names one representative chain through them.
Is this PERT chart maker free?
Yes — free, no signup, and no watermark on the PNG. Vector SVG and HD 2×/3×/4× exports are Pro features.
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