Why this isn't your usual retirement calculator
The "years funded" headline is the honest version of "are you on track?" A 25-year retirement on a 30-year plan sounds fine until you realize one bad market decade at the start can blow it up. The lifestyle tier panel shows that even a small drop in target (lean vs deluxe) buys you a decade of runway — useful when deciding between "retire at 60 and travel less" vs "work to 67 and live well".
FAQ
Where do the 60 / 90 / 130 multipliers come from?
They're a practical shorthand, not a universal rule. The 60% "lean" reflects the common Bureau of Labor Statistics finding that working-age households spend about 70–80% of pre-retirement income, dropping the work-related categories (commute, clothing, retirement contributions) but keeping healthcare higher. The 90% "comfortable" leaves modest room for travel and hobbies. The 130% "deluxe" covers early retirement with more travel or a mortgage still in play.
Why split pre- and post-retirement returns?
Because asset allocation typically shifts from equities-heavy to bonds-heavy at retirement. A 7% pre-retirement return is a reasonable assumption for a 70/30 portfolio; a 4% post-retirement return is more honest for a 50/50 or 60/40. Using one number for both overstates the runway you actually have.
Why does Social Security get added to "need" instead of subtracted from the portfolio drawdown?
Because that's how it actually works in your checking account. You "need" $60k/yr to live; Social Security delivers $18k/yr; the portfolio has to make up the remaining $42k/yr. Modeling it the other way (subtracting from a target) buries the real drawdown rate. The way this tool shows it, the headline "years funded" is the number of years the portfolio can carry that $42k gap, not the full $60k.
Methodology
Accumulation phase: year-by-year compounding at the pre-retirement return, with the user contribution and employer match added at the end of each year. At retirement, balance is converted to a real (today's-dollar) amount by dividing by (1+inflation)years_to_retirement. Drawdown: portfolio must cover (desired income − Social Security − other), growing with inflation each year, while still earning the post-retirement return. The portfolio is depleted when the inflation-adjusted annual drawdown exceeds the inflation-adjusted balance × (return − inflation) — i.e. when the 4% rule's safe-withdrawal assumption breaks.