Who is in two places at once?
Load per person across the schedule, then levelling that spends only the float you already have — and says plainly when there is not enough.
Who is committed to two things at once
Load per person across the schedule, and levelling that uses only the float you already have.
Activities
Same predecessor syntax as the critical path calculator. Put one or more owners in the last column, comma-separated.
Load, as planned
After levelling
Work with float is delayed within that float. Nothing critical is touched, so the finish date does not move.
What was moved
How loading and levelling work
Loading. Effort is spread evenly across each activity's duration. An activity with two owners is treated as shared between them, not as requiring full effort from each — assuming otherwise silently doubles the people a plan needs.
Levelling. Activities are considered least-float-first, since the most constrained work is hardest to place and should be positioned while there is still room. Each is delayed only within the float it genuinely has.
The objective is stated because it has to be: remove overload using existing float, without moving the finish date. A different objective — say, minimise peak load at any cost — produces a different and equally valid answer. There is no single correct levelling, and a tool that presents one without saying what it optimised for is hiding the interesting part.
Overload that cannot be fixed within float is reported, not hidden. Silently extending the project to tidy the histogram would answer a question you did not ask.
The flat histogram is a simplification
Effort here is spread evenly across an activity's duration. Real work is front-loaded, back-loaded or lumpy, so a level-looking chart can still conceal a genuine peak.
What this reliably catches is the structural problem: one person committed to two activities across the same days. That is an arithmetic fact about the plan rather than a judgement about how they will organise their week, and it is the version worth acting on.
Float is a shared resource
Levelling spends float. An activity moved to resolve an overload has less room left for anything else that goes wrong, and the plan is more fragile afterwards even though the finish date is unchanged.
That is a real trade and it is worth making deliberately. A perfectly level histogram with every activity pushed to its late start is a plan where nothing can slip at all.
When levelling cannot fix it
If overload survives, there are only four honest responses: add capacity, cut scope, accept a later finish, or accept the overload and its consequences. This tool does none of them for you, because each is a decision with costs that arithmetic cannot weigh.
What it will do is tell you plainly that the plan as written requires someone to be in two places, which is more useful than a smoothed chart that implies otherwise.
Capacity above one
A capacity of 2 means two interchangeable people working under one name. That is a reasonable model for a pool of similar skills and a poor one for two specialists who cannot cover each other — in the second case, model them separately, or the plan will look feasible and will not be.