FatFIRE Math

Calculator

Test a retirement beginning in any historical year.

Choose a starting year, portfolio, annual spending and allocation. The calculator applies each subsequent year's return and inflation, then compares the result with other starting years in the record.

The retirement

Today's dollars. Inputs stay in this browser.

1966 Any year from 1928 to 1995 — the last one the record can follow for 30 full years.
Raised with inflation every year after the first. That is a 4.00% withdrawal rate.
Allocation
Stocks with a fifth in 10-year Treasuries — the usual Fat FIRE accumulation mix.
Jump to a year that mattered:
30 years later Ran out in 1992 In today's money, after everything was spent.
Lowest the portfolio got $0 The moment it would have been hardest to hold your nerve.
Starting years that held 65 of 68 Same portfolio and spending, every other start year on record.
Spending that survived them all $114,705 A 3.82% withdrawal rate — the most this portfolio could have taken and never failed.

Retiring in 1966 with $3,000,000 and spending $120,000 a year, the money ran out in 1992 — 26 years in, with 4 years still to fund.

Exhibit 1 — the portfolio, year by year Real dollars
A $3.0M portfolio retiring in 1966, spending $120k a year$0$2.0M$4.0MStarted with $3.0M1966197619861996
Each step is one calendar year: the withdrawal comes out, then that year's real return is applied to what is left. The dashed line is the portfolio you started with, so anything below it is a retirement that is behind where it began.
Exhibit 2 — how every other start year ended Rust bars ran out of money
What the portfolio was worth at the end, by the year the retirement started$0$5.0M$10M194019601980
One bar per starting year: what was left at the end. Your year is the green one. Bars are capped at four times the starting portfolio so the failures stay legible.
Start Year Lowest point Ended with
Your year — retired in 1966Lasted 26 years. 1966 $0 Ran out in 1992
The median startNever once dipped below the starting portfolio. 1950 $3,000,000 $8,535,327
Best start on recordNever once dipped below the starting portfolio. 1985 $3,000,000 $18,268,960

Pre-tax and before fees. Withdrawals are taken at the start of each year and raised by that year's actual inflation. Need a portfolio figure first? Start with the Fat FIRE number calculator.

Why the starting year matters

Withdrawals taken after an early decline sell more of the portfolio at lower prices. The remaining balance then captures less of a later recovery. Compare starts in the 1960s and 1980s to see how the order of returns changes the result.

Why the first five years matter → How much of a Fat FIRE portfolio belongs in stocks? →