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The boring-money tool · public

Boring, and it works.

The private finance tools in the lab keep proving one small thing, so here it is in the open: put a little in, leave it alone, let time do the math. $300 a month in a low-cost index fund, around 7% a year, for 45 years — one working life, first paycheck to retirement — grows to about $1.14 million. No trick, just compounding. Change the numbers below and watch.

The calculator

Your turn — play with it.

Your plan

$
What you begin with today. Zero is fine.
$
What you add every month. A negative number means you're drawing down.
%
A long-run low-cost index fund is often modeled near 7–10% a year. Not a promise — an assumption.
years
How long you let it sit. Time is the ingredient that does the most.
After that time, you'd have
$1.14M
Based on a steady 7% a year, compounded monthly.

🫧 That's millionaire territory — mostly from money you never earned, just growth on money that sat still.

What you paid in
$162,000
What growth added
$975,778
What you'd have What you paid in
Why this works

Why boring wins.

Nothing here is clever. That's the whole point — and it's the same standard the lab holds its private tools to.

Time does the heavy lifting

In the default plan, most of the final number is growth — not the money you put in. Start earlier, and time quietly outworks a bigger paycheck.

Boring beats clever

The lab's backtest tools graded eleven years of trying-to-be-clever against simply staying put. The dull verdict: doing nothing won.

Just math, not advice

This is a calculator, not a plan for you. It assumes one steady return; real markets rise and fall. What it shows is the shape, not a promise.

The honest fine print. This tool assumes a single, constant annual return compounded monthly, with contributions added at each month's end. Real markets don't move in a straight line — they swing, sometimes for years. The figures ignore taxes, fund fees, and inflation (a million dollars in 45 years buys less than a million today). Past performance is never a guarantee of future results. Nothing here is personalized financial advice; for that, talk to a licensed advisor. It's a picture of how compounding works, meant to be played with — nothing more.