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How your retirement paycheck is calculated

Last updated September 19, 2026

Your retirement paycheck is the highest monthly amount, after tax, that your savings can produce and still last to your planning age (95 unless you change it) in 90% of simulated retirements.

Here's how that number is found. Every year's market return is drawn from U.S. history (1928 through 2025, using the S&P 500's total return and the 10-year Treasury) and blended by your stock/bond mix. Your balances grow or shrink with those returns, your contributions are added until you retire, and from retirement on, your spending, Social Security, pension, taxes, and required distributions play out year by year.

Finding the paycheck is a search, not a single run. MangoDime tries a spending level, simulates 1,200 retirements at it, and asks what share lasted; then it tries again, higher or lower, sixteen times over, closing in on the most you could draw and still clear 9 in 10. That is around 19,000 simulated retirements behind the one figure. Every trial of the search faces the same market history, so what moves between them is the spending, not the weather.

The chance of success on your dashboard, and the percentile bands on the charts, come from a separate 5,000-run pass over your plan as it stands.

Because the returns are drawn from real years rather than one average, a bad stretch early in retirement shows up in the result: the thing a straight-line calculator can't see.

Everything is in today's dollars. The simulation removes inflation from each year's return before compounding, so a $4,100 paycheck means what $4,100 buys now.

Same inputs, same answer: the simulation is seeded from your inputs, so it doesn't drift between visits or devices.