HOW IT WORKS · 90 SECONDS TO YOUR PROJECTION
Five inputs. Ten thousand simulated futures.
No account, no data linking, no upsells. Just the math, with every assumption visible.
STEP 1
What you tell us
Your age
Your current age, in completed years. Drives the simulation horizon and the first-claim Social Security window.
Spouse age (if applicable)
Your partner's current age. We model two coordinated retirements — including survivor benefits.
Combined retirement savings today
Total in 401(k), IRA, Roth IRA, HSA, and any taxable brokerage accounts marked for retirement.
Monthly contribution
Your contributions plus any employer match. We grow this with assumed wage inflation each year.
Monthly spending in retirement
Total monthly outflow you expect: housing, food, healthcare, taxes, travel — everything.
STEP 2
We replay 1928–2025 market history, 10,000 times.
Each of 10,000 simulated futures samples a real historical sequence of monthly market returns and inflation — so the volatility, the bear markets, and the inflation shocks are all genuine, not fabricated. Your contributions grow during your working years; your portfolio gets withdrawn from in retirement; Social Security kicks in at the claim age you choose.
Returns and inflation are sampled as a pair from the same month of history, so when the engine sees a bad inflation year it also sees that year’s real returns — not a cheerful synthetic average that happens to never be true. The whole simulation runs in your browser, in a Web Worker, and finishes in under 800ms.
Y-axis scaled to median path’s peak. Some simulations exceed this range.
STEP 3
What you get back
The same four headline numbers professional planners look at — plus the tabs to drill into each.
Success probability
87%
Share of 10,000 paths in which you don't run out of money before age 95.
Median nest egg
$2.3M
The 50th-percentile portfolio balance at retirement (in today's dollars).
10th percentile
$890K
The downside case — what your worst 1-in-10 paths leave you with at retirement.
Depletion age
Age 91
When the worst 10% of paths run out. "95+ (no depletion)" if even your tail survives.
WHEN YOU’RE NOT ON TRACK
We tell you exactly how to get there.
Three concrete fixes, ranked by effort. No vague “save more” warnings.
Option A
Contribute $340 more/month
Bumps the success probability from 87% → 95%. Same retirement age, same spending target.
Option B
Retire 14 months later
Same contributions, same spending — but compounding has 14 more months to do its work.
Option C
Delay Social Security to 70
Your monthly check grows ~24% versus FRA. Bridges with savings until 70.
WHAT WE DON’T DO
The negative-positioning, in three lines.
We don't link to your bank or brokerage — your data stays in your browser.
We don't recommend specific funds, ETFs, or advisors.
We don't sell to financial advisors who pay for leads.
Honest negative-positioning is what separates Yearfold from the advisor-funnel calculators.