No. 05 — Data & Tools
Millionaire calculator
Enter what you have, what you invest each month, and the return you expect. The calculator solves for the date you cross $1,000,000 — and shows how much of the million you actually pay for.
Choosing an honest return assumption
The US stock market's long-run average is roughly 10% per year before inflation and about 7% after it. Using 7% keeps your target in today's purchasing power — a million that still feels like a million. Assumptions above 8% are optimism, not planning. The reasoning is unpacked in compound interest and index funds.
If the date is further away than you'd like
You have exactly three levers, in order of typical impact: raise the monthly number (increase your income, savings rate), start with a bigger base (how to save $100k), or extend the horizon by starting now rather than later. Doubling the monthly contribution shortens the trip far more than nudging the return — and unlike returns, it's fully under your control.
What the calculator assumes
A constant return compounded monthly, contributions at each month's end, and no taxes — a fair approximation for money inside a 401(k) or Roth IRA. Real markets deliver the average unevenly, so treat the output as a planning date, not a promise. For typical timelines at different savings rates, see how long it takes to become a millionaire.