A FIRE Calculator for People Approaching Retirement: What to Track

The last five years before retirement are when a FIRE calculator starts lying to you in small, expensive ways — the inputs you used at 40 no longer describe the risk you're carrying at 60. The Federal Reserve's 2022 Survey of Consumer Finances puts the conditional mean retirement-account balance for families aged 55–64 at $537,560, with a conditional median of $185,000.^[] Those are the two starting points most people run through a calculator; both deserve more than a blanket 4% withdrawal assumption.

A FIRE calculator built for this life stage should answer one question better than the generic ones do: given what you have, how much annual income can you safely spend? The answer depends on four inputs a 40-year-old's version of the same tool usually ignores — Social Security claim timing, Required Minimum Distribution age, a realistic safe withdrawal rate, and a sequence-of-returns stress on the first five years of drawdown.

Why generic FIRE math breaks five years from retirement

The canonical "4% rule" is an early-retirement abstraction. Morningstar's 2024 review of safe withdrawal rates pegs the starting-year safe figure at 3.7% for a 30-year horizon and a 60/40 portfolio, at a 90% success threshold.^[] Anchoring on the old 4% number overstates your annual safe income by roughly 7–8% — a gap that compounds into real lifestyle decisions you'd rather not undo at 72.

The other asymmetry is time. A 35-year-old who overestimates their FIRE number has two decades to correct; a 62-year-old who overestimates has, realistically, one market cycle. That's why sequence-of-returns risk — the chance that a bad return year lands right at the start of retirement — dominates this window.

The numbers that actually matter when you're close

Full Retirement Age for anyone born in 1960 or later is 67, not 65 or 66 as many older planning tools still assume.^[] Claiming earlier reduces the monthly benefit permanently; delaying past FRA adds roughly 8% per year in Delayed Retirement Credits — but only through age 70, after which the credit stops accruing.^[]

Required Minimum Distributions now begin at age 73 for anyone turning 72 after December 31, 2022, under SECURE 2.0, and they move to 75 in 2033.^[] A FIRE calculator that still defaults to 70½ or 72 is modeling an extra 1–3 years of compounding that the tax code no longer gives you.

What to plug into a FIRE calculator for people approaching retirement

Most pre-retiree calculators skip the levers that actually move the outcome. At minimum, the inputs that belong on the form are:

1. Current real balance across 401(k), IRA, HSA, and taxable — separated by account, because the tax treatment in retirement is not uniform.
2. Years to retirement and Social Security claim age as separate fields; the second is worth an explicit decision, not a default.
3. Real return (not nominal) and a dialed-down SWR (3.3%–3.7% is a defensible range for a 30-year horizon, per recent research).^[]
4. Pension or annuity income as an additional fixed stream, reducing the portfolio draw requirement.
5. A sequence-of-returns sanity check — rerun the projection with the first five years compressed by 25% and see if the plan still works.

How MFFT handles the last stretch

The FIRE tooling inside MFFT splits the projection into two layers: an accumulation phase (the contributions-plus-return math most calculators do well) and a decumulation phase that integrates Social Security, pension income, and RMD-forced distributions. For a pre-retiree, the decumulation layer is where the decisions live. Pair it with a monthly balance-sheet view of the last five working years and you get a planning loop that matches the actual cadence of decisions at this stage — quarterly rebalancing, an annual SWR reset, a cash-ladder check a year out from the intended retirement date.

The calculation rendered below makes the cost of SWR conservatism concrete. Starting from the 2022 SCF mean balance for families aged 55–64 ($537,560) and projecting five years of 5% real growth, the safe annual income spread between a 4.0% and a 3.0% starting withdrawal rate is $6,859. That's the dollar value of your assumption, not a rounding detail.

The single mistake that breaks most pre-retiree projections

Treating the 4% rule as a floor rather than a ceiling. The rule came from William Bengen's 1994 analysis of U.S. market history and assumed a 30-year horizon, a specific 50/50 stock/bond mix, and inflation-adjusted withdrawals.^[] Modern retirees face longer horizons (25-year+ expected retirements are now typical), different bond yields, and wider return dispersion. The Morningstar 2024 update puts 3.7% at 90% safety and 3.3% at 99% safety for the same 30-year window — a meaningful retreat from the old default.

If a pre-retiree FIRE calculator's output is unchanged whether you enter 4.0% or 3.3%, something is wrong with the model. The inputs the tool makes hardest to reach — sequence-of-returns sensitivity, explicit SWR dial, account-by-account tax layering — are the ones that actually move the safe-income number at this stage.

What I'd actually track in the final five years

A pre-retiree's dashboard is most useful when it surfaces four moving numbers on a single screen: real portfolio balance (not nominal), projected safe annual income at your chosen SWR, the gap between that income and your modeled retirement spending, and the current withdrawal rate the portfolio would need to cover the gap. When those four lines converge — projected safe income meets modeled spending at a defensible SWR — the math says you're there. Until they do, one more year of contributing-and-deferring is usually worth more than a 1% portfolio optimization.