How to use this investment calculator
- Choose what to solve for. “End amount” projects your balance. The other options work backward from a target: the contribution, return rate, starting amount or number of years you need.
- Enter your starting amount and regular contribution, and pick whether you contribute monthly or once a year.
- Set the number of years and an average annual return. Use a return after fees, and try a lower rate to see a cautious case.
- Fine-tune the details under “Contribution timing, compounding & inflation”, then read the breakdown, chart and year-by-year schedule. Copy the link to save or share your scenario.
Investment growth formula
The end balance is the starting amount grown at the average return, plus the future value of every contribution:
FV = S(1 + i)^n + C × ((1 + i)^n − 1) / i × (1 + i·t)
- FV
- end balance (future value)
- S
- starting amount
- C
- contribution per period (month or year)
- i
- return per contribution period = (1 + r/m)^(m/p) − 1, where r is the annual return, m the compounding periods and p the contributions per year
- n
- number of contributions = years × p
- t
- 1 if you contribute at the beginning of each period, 0 if at the end
Worked example
With $10,000 to start, $500 at the end of each month and a 7% return compounded annually, the monthly return is i = 1.071/12 − 1 = 0.5654%, and 20 years means n = 240 contributions. Then (1 + i)n = 3.8697, so the starting amount grows to $10,000 × 3.8697 = $38,697, and the contributions grow to $500 × (3.8697 − 1) ÷ 0.005654 = $253,768. The total is $292,465: $130,000 you put in and $162,465 of earnings.
Every “solve for” option uses the same equation, rearranged the way spreadsheet functions do it: PMT for the contribution, PV for the starting amount, RATE for the return and NPER for the time. The time is rounded up to the first month (or year) in which your balance actually passes the target.
What rate of return should you expect?
U.S. large-company stocks (the S&P 500 with dividends reinvested) returned an average of about 10% a year from 1928 through 2025, or about 6.8% a year after inflation, according to data compiled by NYU Stern professor Aswath Damodaran. In the same dataset, 10-year U.S. Treasury bonds returned about 4.5% a year from 1928 through 2025. Those are long-run averages, not promises: the S&P 500 lost money in 26 of the 98 calendar years from 1928 through 2025, including a 36.6% loss in 2008 (dividends included).
That is why this calculator starts at 7%, below the stock market’s historical average: a portfolio that holds bonds or cash has earned less than stocks alone, fees come out of your return, and future returns may be lower than past ones. The SEC’s investor education site notes that every investment carries some risk and that higher potential returns generally come with more risk. If your goal is only a few years away, a lower rate is more realistic, because a bad year leaves little time to recover.
How much to invest each month to reach $100,000, $500,000 or $1 million
Monthly contribution needed, starting from $0, with deposits at the end of each month and returns compounded annually (no fees or taxes). Reaching $1 million in 30 years takes about $710 a month at 8%, but $1,757 a month if you have only 20 years.
| Goal | At 6% a year | At 8% a year |
|---|---|---|
| $100,000 in 10 years | $615.49 | $555.17 |
| $100,000 in 20 years | $220.54 | $175.75 |
| $100,000 in 30 years | $102.62 | $70.99 |
| $500,000 in 10 years | $3,077.43 | $2,775.86 |
| $500,000 in 20 years | $1,102.69 | $878.74 |
| $500,000 in 30 years | $513.08 | $354.97 |
| $1,000,000 in 10 years | $6,154.85 | $5,551.72 |
| $1,000,000 in 20 years | $2,205.37 | $1,757.47 |
| $1,000,000 in 30 years | $1,026.15 | $709.95 |
How much will $10,000 grow?
What a one-time $10,000 investment is worth after each period at different average annual returns, compounded annually with nothing added:
| Years invested | 4% | 6% | 8% | 10% |
|---|---|---|---|---|
| 5 years | $12,167 | $13,382 | $14,693 | $16,105 |
| 10 years | $14,802 | $17,908 | $21,589 | $25,937 |
| 15 years | $18,009 | $23,966 | $31,722 | $41,772 |
| 20 years | $21,911 | $32,071 | $46,610 | $67,275 |
| 30 years | $32,434 | $57,435 | $100,627 | $174,494 |
| 40 years | $48,010 | $102,857 | $217,245 | $452,593 |
Time matters as much as the return. Investing $500 a month at 7% for 40 years instead of 30 grows to $1,235,771 rather than $584,726, although the extra 10 years add only $60,000 of contributions.
Inflation-adjusted (real) returns
A dollar in 20 years will buy less than a dollar today. To convert a nominal return into a real return, use real return = (1 + nominal return) ÷ (1 + inflation) − 1. At 7% with 3% inflation, the real return is 3.88%, a little less than simply subtracting the two. U.S. consumer prices rose an average of 2.5% a year from 1995 to 2025, based on Bureau of Labor Statistics CPI-U annual averages.
The calculator shows your end balance in today’s dollars using the inflation rate you enter. In the default example, $292,465 after 20 years would have the buying power of about $161,931 today. Use that figure when you compare the result with today’s prices or income. For more on how prices change over time, see our inflation calculator.
How fees affect your returns
Fund expense ratios and advisory fees are charged on your whole balance every year, so small differences compound. The SEC’s Investor.gov shows $100,000 growing 4% a year for 20 years ending at about $208,000 with a 0.25% annual fee but about $179,000 with a 1% fee. Here is the same effect on $10,000 plus $500 a month for 30 years at 7% before fees:
| Annual fee | Balance after 30 years | Cost of fees |
|---|---|---|
| No fee | $660,849 | $0 |
| 0.1% | $647,195 | $13,654 |
| 0.5% | $595,615 | $65,234 |
| 1% | $537,455 | $123,394 |
Moving from a 1% fee to a 0.1% fee would leave you $109,740 more after 30 years. We model a fee by reducing each year’s return to (1 + return) × (1 − fee) − 1; this reproduces the SEC example above. To use the calculator with fees, enter your expected return minus your total annual fees.
Dollar-cost averaging
Investing the same amount at regular intervals, whatever the market is doing, is called dollar-cost averaging. Because the dollar amount is fixed, you automatically buy more shares when prices are low and fewer when they are high, and a steady routine can help you manage risk and stick with your plan. Contributing a set amount from every paycheck to a 401(k) works this way.
This calculator assumes a steady average return, so it shows the effect of your contributions but not of market swings. Dollar-cost averaging does not prevent losses when prices fall. If you already have a lump sum, investing it at once gives it more time in the market, while spreading it out lowers the risk of investing everything just before a decline.
How to reach your investment goal faster
- Start as early as you can. Each extra year of compounding adds more than the year before.
- Raise your contribution. In the default example, $100 more a month adds $50,754 over 20 years.
- Use tax-advantaged accounts such as a 401(k) or IRA, and capture any employer match. Our 401(k) calculator models the match and contribution limits.
- Keep costs low. A lower expense ratio leaves more of the return in your account.
- Check your plan against retirement needs with the retirement calculator, or compare savings rates with the compound interest calculator.
Frequently asked questions
How do I calculate the future value of an investment?
Grow the starting amount by (1 + i)n and add the future value of your contributions, C × [(1 + i)n − 1] ÷ i, where i is the return per contribution period and n is the number of contributions. For example, $10,000 plus $500 a month for 20 years at 7% grows to $292,465: $38,697 from the starting amount and $253,768 from the contributions.
How much do I need to invest each month to have $1 million?
Starting from zero, you need about $710 a month for 30 years at an 8% average annual return, or $1,026 at 6%. With 20 years, the amounts rise to $1,757 and $2,205 a month. Time does most of the work, so starting early lowers the monthly amount sharply. Returns are not guaranteed, so saving a little more than the minimum builds in a cushion.
How much will I have if I invest $500 a month for 30 years?
At a 7% average annual return, $500 a month for 30 years grows to about $584,726, even though you put in only $180,000. At 6% it would be about $487,256, and at 8% about $704,275. These figures assume end-of-month deposits, returns compounded annually and no fees or taxes.
What rate of return should I use in an investment calculator?
Use a long-run average you would be comfortable relying on, after fees. U.S. stocks returned about 10% a year on average from 1928 through 2025, but they lost money in 26 of those 98 years, and a mix that includes bonds has earned less. Testing a lower rate, such as 5% or 6%, shows how your plan holds up if markets disappoint.
How long does it take to double my money?
Divide 72 by the annual return to estimate the years needed to double your money (the Rule of 72). At 7%, that gives 72 ÷ 7 = 10.3 years; the exact answer is 10.24 years. At 10%, the rule gives 7.2 years versus an exact 7.27. Choose “Investment length” in the calculator to solve for any target, not just doubling.
Should I use a nominal or an inflation-adjusted return?
Either works if you are consistent. With a nominal return such as 7%, the calculator also shows the end balance in today’s dollars using your inflation rate: the $292,465 in our example is worth about $161,931 today at 3% inflation. If you enter a real (after-inflation) return instead, results are already in today’s dollars, so set inflation to 0%.
Is it better to invest at the beginning or the end of the month?
Investing at the beginning gives each contribution one extra month to grow, so the balance ends slightly higher. In the default example, beginning-of-month contributions finish at $293,900 instead of $292,465, a difference of $1,435 over 20 years. That is small next to the effect of contributing more or staying invested longer.
How much do investment fees cost over time?
More than they appear to, because fees are charged every year on your whole balance. For $10,000 plus $500 a month over 30 years at 7% before fees, a 0.1% annual fee leaves $647,195, while a 1% fee leaves $537,455: $109,740 less. Compare fund expense ratios and advisory fees before you invest.