After posting the deduplication calculator last time, I got a few questions about source versus target deduplication, and whether the calculator was good for source deduplication scenarios.
The short answer is that it is not.
It is a reasonable tool for estimating target deduplication (with all the caveats that I included last time) but doesn't tackle source deduplication.
So I fixed it.
The tool now deals with source and target deduplication. All the same caveats apply: the tool is primarily useful for instructive purposes, not scientifically accurate sizing of deduplication appliances. It will be more right than wrong, but it may not be right enough to stake your precious budget allocation on. Or your job!