Instant answers to "what could my money grow to?" — pick a lump sum or a monthly contribution and a time horizon to see the projected future value at a 7% return, with charts, scenarios and the formula.
These projections use standard future-value math. A lump sum grows by FV = P × (1 + r)n, while regular monthly contributions grow by the annuity formula FV = PMT × [((1 + i)n − 1) ÷ i]. We default to a 7% annual return — close to the long-run historical average of a diversified stock portfolio — and also show 5% and 10% scenarios on each page so you can see a conservative and an optimistic outcome. Real returns vary year to year and are reduced by taxes and fees, so treat every figure as a planning illustration rather than a guarantee. For a fully custom projection with your own rate, contributions and inflation adjustment, use the investment calculator or the compound interest calculator.
Every figure on this page comes from one equation: future value equals present value multiplied by (1 + r) raised to the number of periods. At 7% a year, $10,000 becomes $38,696.84 over 20 years and $76,122.55 over 30. The extra decade is worth more than the entire first two, which is the whole argument for starting early stated as arithmetic rather than advice.
Regular contributions follow the annuity form instead, where each payment compounds for a different length of time. Investing $500 a month at 7% for 20 years contributes $120,000 and projects to $260,463 — the growth exceeds the contributions, but only past roughly the fifteen-year mark. Before that, most of the balance is simply money you paid in.
The number these projections do not show is inflation. A 7% nominal return alongside 3% inflation is a real return of 1.07 ÷ 1.03 − 1 = 3.88%, so the same $10,000 grows to about $21,911 in today's purchasing power over 20 years, not $38,697. Both figures are correct; they answer different questions, and only the second tells you what the money will buy.
Two habits keep projections honest. The rule of 72 gives a fast sanity check — 72 ÷ 7 suggests about 10.3 years to double, against an exact 10.24 — so a projection that implies a much faster doubling deserves a second look. And a steady annual return is a modelling convenience, not a forecast: real markets deliver the same average through a sequence of good and bad years, and when the bad ones arrive matters enormously if you are withdrawing rather than accumulating.