What is attrition costing you?
Move the sliders to your actual numbers. This is deliberately crude: two inputs, no assumptions about your giving cycle, no model. It’s the back-of-the-envelope version of the question, and it’s usually enough to show whether the real version is worth asking.
A rough estimate, not a model. It sizes the pool; it doesn't name who's in it.
What this does and doesn’t tell you
It tells you the size of the pool. It does not tell you who is in it.
The gap between those two things is the whole job. Most organizations can estimate the number above within a few points. Almost none of them can name the specific people who are about to become part of it while there’s still time to do something about it. That’s a prediction problem, and it’s answerable from records you already have.
If you want to see what that looks like against your own numbers, book 20 minutes or email nate@pydealist.com.