I’ve made a spreadsheet calculator, so anyone can play with it:
Edit: Comparison with historical data:
Edit: I feel like, perhaps, there is some confusion in regards to what this formula is.
Probably as soon as people read “formula” they think of it as something distinct and separate from “hard” data from “real” penetration tests. But, as you can see in this snippet, the output of “formula” is very real and true to real life experimental data.