Long-term Investment Calculator: Maximize Your Future Value & ROI
Use this calculator to find future value, present value or the annual rate behind any lump-sum investment. Plug in three of the four variables, hit calculate, and the script returns the missing figure using standard compound-interest equations. The S&P 500 returned about 10 % annually between 1926 and 2023 (S&P Dow Jones, 2024).
Long-term Investment Calculator
How to use the tool
Select what you need—Future Value (FV), Present Value (PV) or annual Interest Rate (i).
Enter the variables. Example A: PV = $8 000, i = 4 %, n = 15 years. Example B: FV = $100 000, PV = $20 000, n = 30 years.
Press “Calculate”. The answer appears instantly below the form.
Test scenarios. Change one field at a time to see how compounding scales results.
The tool solves for one unknown—FV, PV, annual rate or years—by applying time-value-of-money equations with annual compounding, the same formulas taught in graduate finance texts (Bodie et al., 2021).
How does compound interest grow money?
Interest gets added to principal, and future interest earns on that larger balance, so growth accelerates exponentially; Albert Einstein called it “the eighth wonder of the world” (Investopedia, 2024).
Which variable boosts future value the most?
Extending time usually beats raising rate or principal because each extra year multiplies every prior period’s growth factor $$ (1+i) $$ (Vanguard, 2022).
How do I model monthly or quarterly compounding?
Divide the annual rate by the number of periods per year and multiply years by the same factor; the SEC uses that exact adjustment in its compound-interest worksheets (SEC, 2023).
Does the tool adjust for inflation?
No. Compare the calculated FV with an inflation-adjusted target by discounting at the Consumer Price Index; U.S. CPI averaged 3.1 % over 1923-2023 (BLS, 2023).
How precise is the interest-rate output?
The script rounds the rate to two decimals; feeding more significant digits into FV and PV tightens accuracy because exponentiation magnifies rounding error (Morningstar Methodology, 2023).
Why must years be greater than zero?
A zero exponent wipes out growth, and zero in the denominator breaks the interest-rate formula; validation blocks those math errors (ISO 21378:2020 s.5.2).
Where do the formulas come from?
They follow the present-value algebra in CFA Institute’s curriculum and match the notation in “Investments” by Bodie, Kane & Marcus (2021), making them industry standard.
Is this tool helpful?
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