The one problem that I have whenever I try to use an FI calculator is that our current expenses are not reflective of what they will be around the time when I think we will hit FI. On FIRE calculators, I'm usually asked to enter current income, savings, and spending. Problem is, some of the savings is going towards the kids so can't be used in that calculation and we also will be spending quite a bit less once the kids are gone, even if we take an extra trip each year.

So, this is what I do. For the future spending calculation, I have been subtracting 75% of the amount that is spent on the kids' food, groceries, activities, etc., but I keep travel expenses the same, even though there will be only two of us visiting places instead of 4. I take that final number and then multiply that by 25. Then I use regular retirement calculator that just asks for the current annual savings, current portfolio amount, and the desired final $ number that we think we will need to retire, and use it to find out how many years it will be until FI. It looks like it will most likely be age 45 when using a fairly conservative growth rate.

Okay, have I confused you enough? Am I doing this WAY wrong or is this a fairly good way to calculate FI for us?