Investment Calculator
Project the future value of your investments — with regular contributions, compound returns, and an optional inflation adjustment.
Investment Growth Calculator
Year-by-year breakdown
| Year | Contributed so far | Nominal balance | Real (today's $) |
|---|
How to calculate investment growth
Projecting investment growth combines two ideas: compound returns on the money you already have, and the future value of every new dollar you add along the way. The initial deposit grows at the assumed annual rate of return, compounding over the full term. Each regular contribution also compounds, but only for the time remaining after the date it was made.
The investment calculator above handles both at once. You enter the starting balance, the contribution amount and how often you make it, the annual return you expect, and how long you'll keep investing. The result is the projected final value, the total amount of contributions, and the dollar gain that came from compounding alone. As a compound investment calculator it shows how returns build on themselves; as an investment return calculator or investment estimator it projects where steady contributions could leave you years from now.
For long horizons the share of the final number that comes from returns dwarfs the share that came from contributions. That's the headline lesson of compound interest: small consistent deposits, given enough time, end up vastly larger than the sum of those deposits.
Future value formula
This future value calculator is built on a simple equation. The future value (FV) of a single lump sum compounded annually is:
FV = P × (1 + r)t
where P is the initial amount, r is the annual rate of return (as a decimal), and t is the term in years.
When you add regular contributions, the future value of those contributions is calculated separately and added on top. With contributions of PMT made p times per year, and a per-period effective rate i = (1 + r)1/p − 1, the future value of the contribution stream after n = p × t periods is:
FVcontrib = PMT × ((1 + i)n − 1) / i
The calculator on this page adds FVinitial + FVcontrib to get the total nominal projected value. "Nominal" means before adjusting for inflation; toggle the inflation switch on to also see the value expressed in today's dollars.
What is ROI (return on investment)
Return on investment, or ROI, is the percentage gain on the money you actually put in. The return on investment formula — the ROI formula this ROI calculator uses — is:
ROI (%) = (Final value − Total contributed) / Total contributed × 100
"Total contributed" means the initial amount plus every regular deposit you made over the full term. As an investment ROI calculator, this tool shows total ROI prominently.
How inflation affects your returns
A 7% annual return doesn't translate into 7% more purchasing power if prices are climbing 3% a year at the same time. To find the real rate of return — what you actually get to spend — you use the Fisher equation:
Real return = (1 + nominal) / (1 + inflation) − 1
The shortcut real ≈ nominal − inflation is close but slightly off, especially when both numbers are large; for accurate projections over decades it's worth using the precise formula. This calculator does that automatically when the inflation toggle is on.
The result, expressed in today's dollars, tells you what your future portfolio would buy if prices stayed where they are now. The default 3% reflects the long-run average annual U.S. inflation rate. You can override it to model lower or higher environments — and if you want to see what specific inflation rates have done to the dollar's purchasing power historically, the inflation calculator has the full dataset.