How the investment return calculator works
Enter your starting amount, monthly contribution, expected annual return, number of years, inflation rate and tax rate on gains. The calculator compounds monthly, then shows the future value, how much of it is your own money versus growth, the value after tax on the growth, and the value in today’s dollars.
The formula
Future value = starting amount × (1+r)^n + monthly contribution × ((1+r)^n − 1) / r, with r the monthly return and n the number of months. After tax = contributions + growth × (1 − tax rate).
Returns are not guaranteed and real markets do not grow at a steady rate. This is an illustration, not a forecast or financial advice.
Frequently asked questions
What is compound growth?
Earning returns on your earlier returns as well as on the money you put in. Over long periods it can become the larger part of the total.
What does inflation-adjusted mean?
The future value expressed in today’s purchasing power, after allowing for the inflation rate you enter.
Is the tax figure exact?
No — it applies one tax rate to all growth. Real taxes depend on the account type and how long you hold investments.
Results are estimates for planning, not financial advice. Last reviewed 2026-09-28.