I'm a new reader and just beginning my path of learning and planning. In trying to figure out how much we need to save to retire, I can isolate three major costs that will be eliminated or significantly reduced within 4-15 years of early retirement:

1. I am planning to budget $30,000/year for health care coverage under the ACA during the early retirement period (which I'd estimate to be 15 years, from age 50 to age 65, so $450,000). I expect number this will be be reduced at least in half once we become eligible for Medicare at age 65.

2. We currently have 20 years left on our mortgage. If we FIRE in 10 years, we'd have 10 years remaining, or a mortgage balance of approximately $245,000 (HCOL area).

3. We expect to pay for our children's college education in full (at least the undergrad degree. Grad school can be their responsibility). We've saved up quite a bit already for kids college, but since I expect we can FIRE right about the time our kids are finishing high school, I'd want to budget at least $15,000 for each of our 2 children for 4 years to pay for any remaining college expenses ( $60,000 each or a total of $120,000)

Setting aside those expenses, I estimate we could have a luxurious retirement on $70,000 per year (I know this is not a very mustachian number but we are still new to this, have big travel plans, and live in a very HCOL). Our base non-mortgage, non-child care expenses are around $35,000, plus another $10,000/year to account for home maintenance/car replacement/other predictable or unpredictable "emergencies", with the remaining including funds for travel, entertainment, clothing, restaurants, gift-giving and miscellaneous expenditures)

So, going by the 4% rule, we would need to save $4 million to account for our initial years expenses ($160,000/year ($70,000 plus $90,000 for health care, mortgage, and college)). But is it at all reasonable to just separately budget for those three big items, which would total $815,000? I assume we'd need to account for inflation for the health care expenses, but not for the mortgage expenses or necessarily for the college expenses (since we have 529 savings and I'm just trying to predict the shortfall). I think we would plan to just pay off the mortgage balance once we retire. If I add $15,000 for annual Medicare expenses, beginning at age 65, to our $70,000 budget, we'd need to have $2,125,000 saved in order to draw $85,000 at 4%. If I add back in the $815,000 health care/mortgage/college fund, we'd need to have saved a total of $2,940,000 (plus some amount to account for health care inflation).

So there's a big difference between needing $4 million and needing $3 million to retire! What am I missing? Also, these numbers do not include taxes. So I'd also need to figure out how much we would need to pay in taxes and add that to the total.

I would appreciate any advice/guidance!