The three levers that matter most
Long-term financial planning comes down to three inputs you actually control: how much you save each month, how long you leave it invested, and what return it earns. Of the three, consistent monthly contributions and time in the market typically matter more than chasing a slightly higher return -- an extra 1-2% annual return matters far less over 10 years than starting five years earlier or doubling your monthly contribution.
How to use this calculator
Enter your current savings, a realistic monthly contribution, an expected annual return (a diversified stock portfolio has historically averaged roughly 7-10% before inflation over long periods, though returns vary significantly year to year), and your time horizon. The projection compounds your contributions and growth month by month to show where you'd land. Run it a few times with different contribution amounts to see how much a modest increase now -- even $100-200/month -- changes the ending number over 15-20 years thanks to compounding.
Frequently asked questions
Should I use a conservative or optimistic return assumption? For planning purposes, err conservative (5-7% real return) rather than assuming best-case market years, so you're not caught short if returns disappoint.
Does this account for inflation? No -- the projection is in nominal terms. To think in today's purchasing power, either use an inflation-adjusted ("real") return assumption, or mentally discount the final number by expected inflation over your time horizon.
What should I do once I have a target number? Use it to reverse-engineer a monthly savings rate: if the projected total falls short of your goal, increase the monthly contribution input until it lines up, then treat that number as your actual savings target.