The only thing that actually matters is that you are consistent within your own calculations so that you can compare your year to year results and set reasonable goals.
For our own purposes, we just compare savings to spending and taxes. It is just a matter of interest, as the first time we looked, it was clear that it came to 50/25/25 (it included self employment taxes, so our effective rate looked high). We don't really do anything with these, as our goal is to use all the available workplace programs, and invest the proceeds from RSUs and ESPP, rather than any number.
For discussion purposes, I can then do some math and convert that information into whatever savings rate someone else has defined. There is another active thread where many people are posting both gross and net and it is interesting to see the difference tax rates via that method.
