Investment Calculator – Estimate Your Investment Growth Over Time
Our free investment calculator helps you project how your money will grow over time using compound interest, regular monthly contributions, and a range of compounding frequencies. Whether you're planning for retirement, saving for a major purchase, or simply building wealth, this tool gives you a clear picture of your financial future. Enter your starting amount, expected rate of return, and time horizon to instantly see your estimated returns.
The amount of money you are starting with.
Additional amount you plan to invest every month.
Expected average annual rate of return on your investment.
How long you plan to keep your money invested.
How often interest is compounded on your investment.
Average annual inflation rate to calculate inflation-adjusted returns.
Your results will appear here
How to Use This Calculator
1. Enter your Initial Investment — the lump sum you are starting with today. 2. Enter your Monthly Contribution — any recurring amount you plan to add each month (you can leave this as 0 if you are making a one-time investment). 3. Input the Annual Interest Rate — this is the expected average yearly return on your investment (e.g., 7% for a diversified stock portfolio). 4. Set the Investment Period in years — how long you intend to let your money grow. 5. Choose your Compounding Frequency — how often interest is calculated and added to your balance (monthly compounding is most common for many accounts). 6. Optionally, enter an Inflation Rate to see your returns adjusted for purchasing power. 7. View your results instantly: future value, total contributions, total interest earned, inflation-adjusted value, and effective annual rate.
How the Investment Calculator Works
This calculator uses the standard compound interest formula combined with a future value of annuity formula to account for regular monthly contributions. The result gives you a comprehensive estimate of your investment's growth over time.
Compound Interest Formula
For a lump-sum (one-time) investment, the future value is calculated as:
FV = P × (1 + r/n)n×t
- P = Principal (initial investment)
- r = Annual interest rate (as a decimal)
- n = Number of times interest compounds per year
- t = Time in years
Future Value of Regular Contributions
When you add monthly contributions, the calculator uses the future value of an ordinary annuity formula:
FVcontrib = PMT × [((1 + r/12)12×t − 1) / (r/12)]
- PMT = Monthly contribution amount
The total future value is the sum of both: the growth of your initial lump sum plus the accumulated value of your monthly contributions.
Effective Annual Rate (EAR)
The EAR shows the true annual return when compounding is taken into account, and is calculated as:
EAR = (1 + r/n)n − 1
A higher compounding frequency means a slightly higher effective return — for example, monthly compounding yields more than annual compounding at the same nominal rate.
Inflation-Adjusted Value
To understand what your future money is worth in today's dollars, the calculator divides the future value by the cumulative inflation factor:
Real Value = FV / (1 + inflation rate)t
This helps you set realistic expectations about your purchasing power at the end of your investment period.
Why Compound Interest Is So Powerful
Compound interest means you earn returns not just on your original investment, but also on all the interest you've already earned. Over long time horizons, this creates an exponential growth curve — often called the "snowball effect." Starting early, even with small amounts, can result in dramatically higher wealth due to the power of compounding over decades.