Investment Calculator
Project how a lump sum plus monthly contributions could grow at an expected annual return, with monthly, quarterly or annual compounding.
Enter your starting amount, contribution, return and years, then press Calculate growth.
What the investment calculator does
This tool projects the future value of an investment that begins with a lump sum and receives regular monthly contributions. You enter the starting amount, the monthly deposit, the expected annual return, the number of years and how often the return compounds. It shows the final balance, the total you put in yourself, and the part of the balance that came from growth.
The return you enter is an assumption, not a promise. Markets move up and down, and a fixed annual rate is a simplification. Treat the result as a planning illustration that shows how time, contributions and the rate interact, not as a forecast of what your account will hold.
How to use it
- Enter the starting amount, the money you invest on day one. Use 0 if you begin with nothing.
- Enter the monthly contribution. Each deposit is treated as added at the end of its month.
- Enter the expected annual return as a percentage, such as 7. Enter 0 to see what contributions alone would produce.
- Enter the number of years, a whole number from 1 to 80.
- Choose how often the return compounds: monthly, quarterly or annually. Monthly is the default.
- Press Calculate growth, then compare the final balance with the total you contributed.
Worked example
Start with 10,000, add 500 each month, assume a 7% annual return compounded monthly, and hold for 10 years. The monthly growth rate is 7% divided by 12, which is about 0.5833% per month. Over 120 months, the starting 10,000 grows to about 20,097. The 120 deposits of 500 grow to about 86,543. Together, the final balance is about 106,639.
Your own money totals 70,000, made up of the 10,000 start plus 120 × 500. The growth is therefore about 36,639, which is roughly a third of the final balance. Changing the return to 5% over the same period would lower the final balance noticeably, so it is worth running a few rates side by side before deciding how much to contribute.
Tips and limits
- Try a range of returns, such as 4%, 7% and 10%, to see how sensitive the result is. Over long periods a small change in the rate moves the final balance a great deal.
- The figures are before fees, taxes and inflation. Subtract the costs you expect to pay, and remember that inflation reduces what the final balance can buy.
- The model assumes a steady return and contributions made on schedule. Real portfolios have weak years, and withdrawals during a downturn can change the outcome significantly.
- This is a general calculation, not personal financial advice. A licensed adviser can account for your taxes, goals and tolerance for risk.
Investment Calculator – Frequently Asked Questions
How does the compounding setting change the result?
The annual rate is converted to an equivalent monthly growth rate for the chosen frequency. With the same nominal rate, monthly compounding gives a slightly higher balance than quarterly, and quarterly gives more than annual.
When are the monthly contributions added?
Each contribution is added at the end of its month, after that month of growth. Paying in at the start of each month would give a slightly higher final balance.
Is the expected annual return guaranteed?
No. It is a constant assumption used to project growth. Real returns vary from year to year, can be negative, and are not guaranteed by any investment or by this calculator.
Are fees and taxes included in the projection?
No. Fund expenses, trading costs, inflation and taxes are not subtracted. If you want a net figure, lower the expected return by an estimate of those costs before you calculate.
Why are the years limited to whole numbers from 1 to 80?
The projection runs one month at a time, so the holding period is entered as a whole number of years. The limit keeps inputs within a range that is practical to plan around.