Home > Tried the Coast FIRE calculator (edited)

Tried the Coast FIRE calculator (edited)

May 29th, 2021 at 07:54 pm

I usually get confused and overwhelmed when I try using retirement calculators. That's why I use the 8x rule of thumb as my goalposts for our retirement. But Firefly's post about Coast FIRE made me curious to try that calculator. (

I ran the numbers once, and it said at our current pace we'd reach Coast FIRE in 11 years! That would be incredible!

But then I realized what they meant by "net worth" was total invested. My net worth calculations count the value of our home, so I had to redo it. But, I also realized that initially I had $1500 listed for housing because even after we pay off the mortgage we'll have property taxes and insurance. I forgot that we do intend to still have rental properties, so the money from those should at least offset our housing expenses. Also, I estimated we put aside $2,500 but realized it's closer to $2,700 (conservatively). So I lowered my "net worth," raised retirement contributions, removed the line for housing expenses and tried again.

Here's my attempt at a retirement budget. (Let me know if you see any glaring omissions here.) Keep in mind this is for three adults.

Ideal budget Monthly
Housing $0
Healthcare $1,500
Groceries $1,000
Fun $1,500
Travel $1,000
Utilities $500
Giving $500
Home improvement $500
Gifts $250
Transportation $250
Total monthly $7,000
Annual $84,000

I'm in between my spouses' age, so I used my age but our combined retirement investments.

Current age: 47

Retirement age: 65

Annual spending in retirement: $84,000

Current net worth (retirement balance): $732,687

Monthly contribution: $2,700 (varies, but this is a conservative approximate average)

Investment growth rate: 7%

Inflation rate: 3%

Withdrawal rate: 4%

Coast FIRE number at current age: $1,036,619

Result: You're 12 years from Coast FIRE!

Unbelievable. I only seem to have added one year in my new calculation. Is this telling me at this rate I'll be done saving for retirement by 59 and be able to retire at 65? If so that's amazing, because if you'd asked me when I'd have enough saved I'd've said "never." I'm sure I'm doing something wrong in the above calculations. Can you poke holes in this scenario?

4 Responses to “Tried the Coast FIRE calculator (edited)”

  1. terri77 Says:

    I think we don’t realize how much our investments continue to grow in retirement.

    It is unfortunate how much health care costs in this country. I plan on staying until 57 only for the lifetime health care benefits.

  2. MonkeyMama Says:

    Yes, the power of compounding! I didn't look at the calculator, but I just ran some rough calcs based on the information you shared. I came up with roughly $2.1 mil age 65, which would cover $85K per year expenses with a 4% withdrawal rate.

  3. ceejay74 Says:

    Wow, thanks MM for running those numbers--that is exactly the amount the FIRE calculator came up with!

    & thanks Firefly for sharing that tool. This is the first time I've ever had a glimmer of hope that we could catch up on our retirement savings!

  4. MonkeyMama Says:

    You are nearing the tipping point where your money is working harder than you are. $733K x 4% = $29K investment returns estimated over the next year. While you contribute $32K per year. Soon enough it will flip.

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