About the Investment Return Calculator
This calculator projects an investment forward using a starting amount, regular contributions, and an average annual return. It separates how much you contributed from how much came from growth — the clearest way to see compounding at work.
How it’s calculated
Ending balance = P(1+i)^N + C·[((1+i)^N − 1) ÷ i], where i is the monthly return, N the number of months, P the starting amount, and C the monthly contribution. Total gain = ending balance − everything you contributed.
Example calculation
$10,000 plus $500 a month at an 8% average return grows to roughly $549,000 over 25 years — of which well over half is gain.
Frequently asked questions
What return should I assume?
Long-run stock market averages are often cited around 7–10% before inflation, but returns vary a lot year to year and aren't guaranteed. Try a range to see how sensitive the outcome is.
Does this account for taxes or inflation?
No — it shows nominal, pre-tax growth. Use the Inflation calculator to see future balances in today's purchasing power.
Projections are illustrative and assume a constant rate of return; real investments fluctuate and may lose value. Past performance does not guarantee future results. This is not investment advice.