Free Resource Leveling & Critical Path Scheduler

RCPSP CPM CP-SAT Google OR-Tools Upload your task list and your real headcount, get a schedule your crew can actually work.

What is resource-constrained scheduling?

The critical path method (CPM) takes your tasks and their predecessors and works out the earliest each one can start. Every free CPM calculator does this, and every one of them assumes you can put as many people on the job as the plan asks for. Real projects don't work that way: you have three electricians, and on the days the plan wants five, something has to give.

Scheduling around that limit is the resource-constrained project scheduling problem (RCPSP), and it is genuinely hard — no commercial package solves it exactly. They apply a priority rule instead, and none of them tell you how far the answer sits from the best one available. This tool uses Google OR-Tools CP-SAT to solve it properly, and says plainly whether it proved the schedule optimal or ran out of time trying.

1 How it works

Start from the Excel template. It already contains a worked 21-task renovation, so you can see the exact format before replacing it with your own.

Fill in your tasks, durations, predecessors and how many people each one needs — then list what you actually have on the resources sheet. Don't rename or delete any sheets.

Upload it, pick which question you want answered, and read the chart. Drag any bar to pin it and everything else re-optimises around it.

2 Upload your workbook

⬆

Drop your workbook here

or · .xlsx

What do you want it to do

Download the Excel template (.xlsx, sample filled in)

3 Results

The schedule

Drag a bar to pin that task where you want it — everything else re-optimises around it.

cannot be delayed — moving it moves the finish date has slack pinned by you more of a resource than you have

The colours count the crew you actually have. A task can look like it has slack on paper and still be unable to move, because someone else needs the same people that week — hover a bar to see what is holding it.

Common questions

What is the difference between the two modes?

They are the two ends of the same trade-off. Work within my crew treats your headcount as a hard limit and tells you the earliest honest finish date. Keep my date treats the date as the hard limit and tells you how many people it would take to hold it. The numbers above the chart are the same either way — only the schedule drawn underneath changes.

Why is a task marked as unable to be delayed when it has slack on paper?

Because the colours count your crew. A task can have days of CPM float and still be unable to move, because the people it needs are busy on something else that week. Hover any bar and it tells you what is holding it — a predecessor, or a crew hand-off.

Which predecessor types does it support?

All four, with lag or lead: finish-to-start, start-to-start, finish-to-finish and start-to-finish. Write them the way MS Project and Primavera do — 3, 3FS+2, 5SS, 7FF-1. A bare number means FS with no lag.

Do I need Excel?

The template is an .xlsx and works in Excel, LibreOffice and Google Sheets. It draws its own Gantt bars and works out start dates from your predecessors, so it is usable on its own even if you never upload it here.

Is it really free?

Yes — no signup, no account, no limit on how many times you run it. Your workbook is held in memory only long enough to write the answer back and is never stored.