See how your savings and investments grow over time — from a starting balance, regular monthly contributions, an interest/return rate, and a time horizon. Shows future value, total contributions, and interest earned. No signup, instant results.
How does compound interest work? With regular contributions, future value is FV = P(1+r)n + PMT · [ ((1+r)n − 1) / r ], where P is the starting balance, PMT is the monthly contribution, r is the monthly rate (annual ÷ 12), and n is the number of months. Compounding means you earn returns on your prior returns — so the longer the horizon, the more growth comes from interest rather than contributions.
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Future value = starting balance grown by the compounding factor, plus the future value of each monthly contribution. The calculator compounds monthly using the annual rate divided by 12.
Because you earn returns on your prior returns. Over long horizons, compounding does more of the work than your deposits — which is why starting early matters so much.
Inflation, taxes, and investment fees, all of which reduce real growth. It also assumes a steady return; real markets fluctuate and can lose value in any given year.
That's your choice and depends on your investments. Many people model a range (e.g., conservative vs optimistic) rather than a single rate. This tool is for illustration, not a forecast.