At risk of clogging this thread up (I'll gladly move this conversation to a PM if that's better etiquette?):

- For the mortgage section, I entered both Principal and remaining principal as positive values. Seems to make things work out. Is that right? (Instead of entering them as debts)

- Is it calculating the deduction of our mortgage interest based on cell B53? It appears to be in G26.

- What's PITHI? (Google results only show it's some type of Indian wedding related thing.)

- There's a green box for SL int. (guess) in G12. What's that?

- ~~Time to FIRE doesn't seem to be changing~~ based on my inputs to "current savings", though I can see the "amount needed" at the bottom. What I'm curious about is time to FIRE as of today. The graph jumps around (curve moving left the more I up our savings), but it seems to be "backwards". $600K below FIRE looks like 8 years from now, for instance, but $300K is 12 years from now... Oh, duh. Time to FIRE is an input.

- Is the calculations sheet independent of the others?

I'll answer here unless/until wrist-slapping starts. ;)

Yes, enter both Principal and remaining principal as positive values. Put mortgage in the mortgage row because the tax treatment for mortgage interest differs from other debt interest.

Mortgage interest estimate for itemized deduction purposes is based on the interest rate (cell F49) and the remaining principal (cell I49).

PITHI is Principal, Interest, Taxes, HOA fee, and Insurance. Sometimes people lump all these together and call the sum "mortgage payment", even though Principal and Interest stop when the mortgage is paid while the others continue. The cell is used only to calculate that sum, and can be ignored otherwise.

SL stands for Student Loan. As with mortgage interest, it is estimated based on interest rate and current principal. Green background means you can override the estimate if you have a better one.

Yes, the calculations sheet is independent of the others.

Great questions!