Monte Carlo · 1,000 trials

Glidepath

Enter your plan on the left. Every change re-runs 1,000 randomized market histories and updates the odds, the range of outcomes, and the trade-off table.

Your plan

Money must last to this age to count as a success.
In today's dollars — the model works in real terms.
Estimated benefit in today's dollars. Set to $0 to exclude. Surplus benefit is reinvested.
0%
In any year the portfolio loses money, that year's retirement spending drops by this much.
60%
30%
Stocks Bonds Cash 10%

Blended real return — · volatility — per year

Probability of success

—%

07085100
—
trials kept money to the end
—
median balance at the end
—
typical depletion age in failed trials

Portfolio value over time (today's dollars)

Median 25th–75th pct 10th–90th pct

The shaded fan is the spread across all 1,000 trials at each age — the top edge is the 90th-percentile (best-decile) path, the bottom edge the 10th-percentile (worst-decile) path. Where the bottom edge touches zero, at least 10% of trials have run out of money.

What moves the odds

Success rate out of 1,000 trials for each combination. Green ≥ 85%, amber 70–84%, red < 70%. The outlined cell is your current plan.

Assumptions

All figures are real (inflation-adjusted), so results read in today's dollars. Annual returns are drawn from normal distributions calibrated to long-run U.S. history: stocks 6.8% mean, 17.2% standard deviation; bonds 2.0% / 6.5%; cash 0.5% / 1.0%; stock–bond correlation 0.10. Savings are added and withdrawals taken at the end of each year; the allocation is rebalanced annually. Social Security is treated as inflation-adjusted income from the claiming age on — it offsets spending in retirement, adds to savings if claimed while still working, and any surplus over spending is reinvested. With a spending cut set, spending drops by that percentage in any year the portfolio return is negative and returns to normal after positive years; a trial that runs dry stays failed even if benefits continue. Trials are seeded deterministically from your inputs, so the same plan always shows the same result — use re-roll to see sampling variation. This is an educational model, not financial advice.