How this calculator works
Future value of a lump sum: FV = PV × (1 + r)^n.
Future value of equal yearly payments: payment × ((1 + r)^n − 1) ÷ r. Payments at the start of each year earn one extra year of growth (an annuity due).
The calculator separates growth from what you put in, so you can see how much comes from returns.
Real investment returns vary year to year; a fixed rate is a planning assumption, not a forecast.
Worked example
$10,000 today plus $2,000 a year at 6% for 15 years
- Lump sum grows to about $23,966.
- Yearly additions grow to about $46,552.
- Total: about $70,518 from $40,000 put in.
Questions people ask
How is future value different from compound interest?
They use the same idea. This calculator works in yearly steps; the compound interest calculator handles monthly contributions and different compounding.
Should I adjust for inflation?
For purchasing power, use a real return (expected return minus inflation), for example 4% instead of 7%.
What return should I assume?
Use a conservative figure for your mix of investments, and test a few values to see the range of outcomes.
Do start-of-year contributions make a big difference?
Over long periods, yes: each contribution gets one more year of growth, adding about one year’s return on the payments.
Last reviewed October 2, 2026